This might be a little unorthodox compared to most Poppy builds you'll see (considering that there is no AP boosts, HP boosts, or that ridiculously over rated Trinity Force), but trust me, the amount of kills and wins that this build will earn for you will satisfy anyone. Before you start bashing it, try it first. If you follow the guide that I provide for you, I guarantee that you'll do more than great.
My build focuses mainly on attack speed, life steal, and damage which are all extremely important when using Poppy.
I'd like to also note, before we dive in, that this build is primarily meant for Twisted Treeline. Although I've done extremely well in Summoner's Rift with this build, Twisted Treeline is simply a better place for Poppy to fight due to the tighter space. More walls equal more stuns, and more stuns equal more kills. With this build's dependence on life steal, the player has to utilize the stunned down time of the enemy champions as best as they can.
First, let's introduce Poppy's skills:
Heroic Charge: This is probably Poppy's most effective attack). The most important thing to remember about her charge is that you always want to position the attack so it pushes the enemy up against a wall or piece of terrain. This way, the enemy will not only be stunned, but they'll take a lot of extra damage as well. You can use Poppy's charge to get away from enemies too, if you're in a tough situation, by using it on enemy minions in your path.
Devastating Blow: As Poppy's most powerful attack, as far as damage goes, you want to use this as much as you possibly can when in a battle with another champion. The cool down is quick, and it doesn't cost too much mana, so be sure to use it as much as possible! Using it after stunning the enemy with heroic charge can be very effective as well.
Paragon of Demacia: The speed boost is what you want when you turn on the active of this ability. Use it when you need to run away from an enemy, or when you just need to get somewhere fast. With this build, however, be sure to use it sparingly. Even though it has a quick cool down, you don't want to spam it due to this build's lack of mana.
Diplomatic Immunity: This is one of my favorite ultimate's in the entire game. You can use this defensively or offensively. It works great if you want to grab a kill from a group of enemies - select an enemy that can't hurt you too much and jump into the group, wiping away enemies with low health. Do NOT select the enemy you want to kill (even though it does extra damage) because once the enemy is killed, your shield dies off, and this leaves you vulnerable. Your shield only lasts for a short amount of time, so be sure to get in and out quickly! As for as using this defensively, if you're running away from a few enemies, use it on an enemy that can't slow you or do too much damage to you, and use Paragon to speed away.
Strategies and Items:
When you start out, all you'll need to buy is your Rejuvination Beads and maybe a couple of potions if you want to stay in the lane longer. Early game is pretty simple with Poppy - use Heroic Charge to stun the enemy against a wall, and use devastating blow when you can. Ignite and exhaust should help you grab a few kills in the early game, allowing you to get gold for Berzerker's Greaves and Tiamat. Be sure to try to get the last hit on those minions to pick up gold!
Mid-game is probably when it gets the toughest for this build. You have a decent amount of damage now with your Tiamat, and you can get gold with the splash damage on minions. You won't see some real power until you reach Phantom Dancer in the late game. During this rough part of the game, play defensively, and try to grab kills with your ultimate and then get out fast. Stark's will help a lot once you get enough gold for that.
Now we're in the late game. So far, you should have Tiamat, Berzerker's Greaves, Stark's Fervor, Phantom Dancer, and be working on your Bloodthirster. This is where it gets fun. With this build, you are virtually indestructible with your insanely fast attack speed, lifesteal, and good damage. If you actually get to buy Infinity Edge (which won't happen in most games), then you're even more unbeatable. At this point in the game, you should be able to 1v1 anyone (even Warwick/Udyr/Jax) with no problem. Remember, even in the late game, Heroic Charge's stun is extremely important! And keep spamming your Devastating Blow.
This concludes my build for Poppy. Like I said, it's different than most builds, but if you try it, I promise you won't be disappointed. Thank you for reading, and I hope you enjoy!
Update as of 12/21/2010:
I finally got around to updating my Poppy build since it desperately needed a fix. The patch that changed Malady to give AP instead of life steal threw off the whole momentum of my build. To adapt to these new changes, I pushed Stark's Fervor up to where Malady used to be, and I replaced the slot in which Stark's Fervor was with a Bloodthirster. This way, the life steal lost in the Malady change is replaced, and the final damage output is much larger than before.
I also edited the description to match the item changes, and I slightly changed the runes.
Thanks for all the support everyone who + voted me, and I hope you all can continue owning with this build.
oh and quit whining about no trinity force... srsly...