I will be filling in the description of my build tomorrow (Thursday) some time.

Here's a quick summary of my builds though:

Build 1) Standard AD Build taking ignite with flat damage marks, flat armor seals, flat cooldown reduction glyphs, and flat health quintessences for early to mid game damage, harass, and survivability. This is my recommended build. Consider swapping out the quints for movement speed quints and/or armor penetration quints to suit your tastes.

Build 2) Standard Tanky DPS Build taking exhaust with armor pen marks, flat health regen seals, flat magic resist glyphs, and flat health regen quints for easy lane sustain.

Build 3) Hybridized AD/Tanky DPS Build taking exhaust with armor pen marks, flat armor seals, flat magic resist glyphs, 2 movement speed quints and 1 armor pen quint.

Build 4) Jungle build based off of stonewall008's jungle build for Riven, taking flat damage marks and quints, armor seals, and 21/0/9 masteries. Boots of mobility may be switched out for boots of lucidity, berserker's greaves, or mercury's treads. Credit to stonewall008 for runes, masteries, and starting items: http://www.youtube.com/user/stonewall008

Personally I prefer build 1, but all 3 builds are just food for thought. Build 1 has impeccable AD burst potential with some sustain through lifesteal and some resistances through guardian angel. Build 2 is geared more towards players that want to tank it out for their team but still deal damage. Build 3 aims to be difficult to take down but still deal decent damage through TriForce, though its weak point lies with lack of sustain.

-Hero


Pros / Cons

Pros:
Lane sustain
Heavy early game harass
Easy to farm
Short AoE stun
All abilities stack fairly well with Attack Damage
Mana/energy independent
Fun to play!

Cons:
With my build, you start without much armor penetration until you complete at least a brutalizer
Doesn't really bring anything more to the table than Wukong except a little more damage
Can be difficult to control without practice
Cooldown dependent
Ultimate is a little delayed; easy to miss with


Runes

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My primary rune build consists of 9 Greater Mark of Strengths to provide Riven with bonus attack damage early game. I feel that these runes, combined with Greater Seal of Resilience and Greater Quintessence of Fortitude allow you to harass substantially well and secure kills early game. These AD marks will also help you with your early game farm and allow you to either ignore Doran's Blade or have AD easily in the 70s-80s in early levels.

If AD marks do not suit your tastes, switch them out for Greater Mark of Desolation, though this will make it more difficult for you to secure early game kills.

Finally, if flat health quints don't suit your tastes, consider swapping them out for Greater Quintessence of Desolation or Greater Quintessence of Strength.

Alternative Runes





Other rune builds consist of tankier options such as Greater Seal of Vigor and Greater Quintessence of Vigor to provide substantial early game health regen, Greater Glyph of Warding to provide early game magic resist, or even Greater Quintessence of Swiftness to provide additional movement speed when moving in and out of battle. I don't really view the movement speed quints as necessary, but they tend to synergize well with her battle style and make playing her a bit more fun.


Summoner Spells



I chose Ignite because it acts as a great finisher move against your opponents for both AD and AP carries. Sometimes all you need is that extra boost of true damage to finish your opponent off, and that's what Ignite's for.



I chose Ghost as the main summoner spell for all 3 builds because, while Flash may help you move into position better, Ghost lasts a lot longer and again helps you catch up or run away from opponents and also provides a large boost to your movement speed during team fights.



I don't favor Exhaust as much as I do Ignite because while it can save your *** sometimes in 1v1s or team fights, Exhaust shouldn't really be used defensively, and with Ghost and movement speed quints you shouldn't really need it to catch up to your opponents for an offensive purpose.

Beyond that, Teleport might be a decent summoner if no one else on your team has taken it and you know you're going to have solo top. Clairvoyance shouldn't be taken by Riven, nor should Fortify or Rally. And no one should ever take Revive. Ever.


Core Items (Build 1)

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Personally, I start off with Doran's Blade for the additional health and AD. It helps early-game farming and gives you a little bit of extra survivability and firepower. After that, boots are typically situation. Normally I take Ionian Boots of Lucidity but if the team is heavy in CC I tend to favor Mercury's Treads. I have also swapped in Ninja Tabi if the enemy team is heavy in auto-attackers.

Wriggle's Lantern is a cheap item, provides early game lifesteal, provides armor, provides attack damage, and provides a ward to help you keep an eye on either primary goals or keep a watch out for ganks. I would not recommend swapping this item out, but if you were to swap it Hexdrinker might be a good idea instead.

Frozen Mallet is where your build starts getting good. Your enemies will have a difficult time escaping you, you'll receive a massive amount of health, and you'll have attack damage as well. In my opinion, this item should not be swapped out at all. You could try a Trinity Force instead but the proc on it is not as good as having the constant slow and health that Frozen Mallet gives you.

The Bloodthirster really provides that team-fight sustain that you're looking for. It stacks considerably well with your abilities, and at max farm on Bloodthirster you should have 43% lifesteal by this point. Coupled with the large amount of health you'll have from runes and Frozen Mallet, this item will keep you in the game. It can be swapped out for Stark's Fervor or Black Cleaver, but I do not recommend doing so.

That completes the core items for build 1. After that, I'd strive towards a Youmuu's Ghostblade (or Hexdrinker instead if you don't already have one), and finally a Guardian Angel. Why GA you might ask? I don't recommend buying it if they are focusing you down so hard that you're getting killed over and over again. I DO recommend buying it, however, if you're managing to make it out of team-fights with half or below-half health. This way if they do manage to slay you, you'll have something to keep you alive just a bit longer. If you play your cards right, you should be able to pull off a stun and possibly escape from the team fight with Valor and Broken Wings.


Alternative Items (Build 1)

Build 1 heavily lacks armor penetration, and if your opponents are stacking armor against you you're obviously going to need it. Therefore, I would recommend swapping out either the ghostblade or the wriggle's for one of the following items, as needed:



With this item, you should have all of the armor penetration you need. It'll cut into 40% of the enemy's armor as well as provide you with additional firepower behind your skills. Great overall item when you're lacking in armor penetration.



This item's active is widely underestimated. While it's true that it doesn't provide you with additional damage, it does provide you with a large boost in attack speed. Using its active also provides you with a boost to your armor penetration as well as the additional 100 magic damage per 4 attacks.



Build 1 also lacks magic resistance with the exception of a GA. So, if you're finding that you're dying a little too quickly to enemy AP carries, try this item out. It'll provide you with a shield if you're hit too hard, and it provides AD as well as magic resistance.



If you're really being focused hard by the enemy AP carries or if you're getting CC-locked, try this item out. It basically gives you an insta-cleanse that you can use whenever you get into a bind. It's a cheap item, has an amazing active, and provides you with a decent amount of magic resist. I would swap out GA for this item if having a QSS was essential.


Summary

So to summarize, Riven has potential to be an excellent AD carry, though perhaps is not as efficient as a well-trained Master Yi or Irelia. Riven adds some utility to her team by providing a disrupt in the form of a short, AoE stun. Riven does not have very much natural sustain, so it's important to be decisive on the type of build you want to use on her by providing her with lifesteal or health regen and resistances.

Because Riven has the ability to charge into battle and trade blows with the enemy and still come out alive, she has potential to become a bush terrorist/female version of Garen. By taking proper resistance items as well as a CC-reduction item, she has the ability to sustain herself fairly well in team fights while making it difficult for the enemy to burst or CC her down.

I hope you found this guide informative and please keep in mind that it is still under heavy construction. All constructive feedback is appreciated.

-Hero