So my phone is a HTC Desire that means it runs Android and I will be focusing on what's in the android market, I do care what other people can get on the iphone too though as I might want to share/ compare stats with.
The three apps I've seen so far are
Runkeeper, which I've had installed since I got the phone but never actually used and two other apps I heard about in the comments of runkeeper on the market.
Endomondo and Cardio Trainer.
For me the price, functionality and social networking links are all pretty important.
Price: Winner Emdomondo - free with support for heart rate monitor. Runkeeper and Cardio Trainer both have free versions but you have to pay to unlock some features.
Features: Tie, but Runkeeper has promise to gain more new features. Cardio Trainer has some nice add ons for the notification bar that some may like - it keeps a total of you burnt calories over the week - but I don't want that visible at all times. Endomondo has support for a bluetooth heart monitor and audio cues without having to pay which is good. Runkeeper has the ability to share your runs live if you subscribe to the elite account which would be nice.
Social network support: Run Keeper, lets you share with FB and Twitter instantly and allows you to have street teams which is a group that lets you share stats easily which I like.
Tomorrow I will actually test Endomondo and Run Keeper at the moment I'm leaning towards Run Keeper because their website seems great.