Plants vs. Zombies Adventures is a Facebook based social game, defence game, free to play on Facebook, from PopCap.
" Go beyond your yard and discover more plants, more zombies, and new challenges. Battle zombies in town or on a road trip — but beware: now zombies will take any path possible to get your brains. Challenge your friends by sending zombies to invade their towns, and see where your stack of zombies ranks on the leaderboard. And with constant updates, you’ll find surprises around every corner. It’s a thrilling new way to live, grow and zap zombies on Facebook. "