Interested in browser-based RPGs? Wanna kill zombies? I have a treat for you! Of all places, I found this little gem on Yahoo! Games. It's called Zombie Pandemic, and is quite literally one of the best web-based RPGs I've ever seen.
Scavenge, fight and explore your way through a city decimated after the zombie apocalypse. Join a clan and build safehouses on the map. Really, this is a must-try game!
Check it out for yourself at http://games.yahoo.com/game/zombie-pandemic