We've had our fun with Zombies, Run! before. The fitness program/zombie horde simulator is one of the more innovative ways we've seen to get in shape. However, it's not all casual fun. Sometimes you have to get serious. If you're looking for an app to push you a bit harder, you may want to check out Zombies, Run! 5K Training. Currently on sale for $0.99 in the Play Store (75% off), this one gives you more in-depth structure to get you through a full 5K in 8-weeks.
There's a lot of run tracking apps out there, and you could be forgiven for forgetting about Google's very own My Tracks, what with its complete lack of zombies. But the dedicated runner or cyclist might want to give My Tracks a second glance, since it just got a major overhaul and (more importantly) it's still free. The biggest addition to the open source app is a user interface that plays nice with Ice Cream Sandwich, and presumably, Jelly Bean.