This is just a build I made for funzies after playing Vladimir for a while. I personally love it considering how endgame you still deal decent damage and you're pretty much invincible.

Quintessence of Fortitude: The flat health gives you a lil' bit of ap but they're mainly for early game survival
Mark of Insight: Magic Pen runes up your damage throughout the entire game
Seal of Vitality: The Health per level runes are mainly for endgame
Glyph of Focus: Flat CD reduction runes help you spam your Q more which helps with harassing and survival

I choose to start off with an Amplifying Tome/Potion instead of a Doran's Shield so that you can upgrade it into a Hextech Revolver ASAP. The Reason for this is your E drains a decent amount of life to use, and you want to maintain a 4 stack as much as possible so you hit harder and heal more.
Next go for Sorcerer's Boots for the Magic Penetration

Here's where my build goes astray from most builds.
Vlad has the unique passive ability to turn ability power into health and vice versa.

After boots I like to build either Zhonya's Hourglass or an Abyssal Scepter, usually Zhonya's for the invulnerability, but you may want to build the Scepter if going against an AP champ thats doing well. The reason for this is with these 2 items you're getting 5 different stats:
1. 170 Ability Power
2. 306 Health from your passive
3. 50 Armor
4. 57 Magic Resist
5. An aura that reduces enemy champions Magic Resist by 20
As you can see at this point you're not only going to be hard to kill, but you'll also be doing a nice bit of damage as well

At this point I like to finish my Will of the Ancients so that anybody who uses AP on your team will love you for the +30 Ability Power, +25% Spell Vamp, and the Debuff reducing enemy champions magic resist by 20. As you can see these two buffs alone will greatly encourage team fights and should tip the scales in your favor

Now I have one word to describe why I love Vladimir. Versatility. At this point since you've built both defensively and offensively you can either continue building both, or focus on one.

If your team is obliterating I'd advise going down the nuke road to continue to shut them down. I'd recommend;
Rabadon's Deathcap: The +155 Ability Power and the +30% increase to your AP = win
Void Staff: the 40% Magic Penetration makes you hit like a truck

If both teams are doing comparatively well I'd start building items with both health and a defensive stat

Health/Armor if an enemy AD champ is doing well
Sunfire Cape: Extra damage just for standing next to someone? awesome
Randuin's Omen: This is my favorite to counter champs like Master Yi/Xin Zhao/ or any AD champ that build Attack Speed just because it doesnt rely on the enemy attacking you. By activating it + Sanguine Pool you can really save someone's @$$

Health/Magic Resist if an enemy AP champ is doing well
Banshee's Veil: Every 45 seconds you negate an enemy spell pretty self explanatory how awesome that is.
Spirit Visage: This item is amazing for Vladimir and can be built early if desired at only 1550 gold you get health MR CDR and Makes your Q and Spell Vamp heal you for 15% more than it would normally

Health/AP
Rylai's Crystal Scepter: Health/AP/Slow is great for 1v1 against any champ

Now if there's someone on thier team that likes to find your teammates and melt their face you should probably build against them so you can turn the tide

Thornmail: I personally don't like this item because you have no way of making the enemy champion focus you like a taunt plus the amount of damage it'll do will be negligible unless they are 3 shotting your teammates, however the massive amount of armor is always nice plus it's only 2000 gold.
Force of Nature: Scenario: Early game - bot fed Annie, Midgame - top fed Annie Solution? start off with a Banshee's Veil to mitigate enough of the damage so that you can push her away from your troops, then build FoN so that you can pop in and out of the fight to harass - regen - harass - regen - repeat until she either runs or she's low enough that you can pop your R->E->Q->Ignite->W for the kill