Hey all,
With the explosion of smart phones in the past year or so there have been a lot of great fitness apps released. Thought I'd start a thread on what some of the favorites are.
My favorite so far is Cardio Trainer on my DroidX. I haven't checked but I think it might be an Android specific app. I did a quick browse on my iPhone (yes I have both) and didn't see it in the app store.
First of all Cardio Trainer was the first fitness app I tried that didn't kill the phone's battery in about an hour. I've actually gone on four hour rides and not come close to killing a completely charged battery. Also it will automatically upload your workout (I think to several different sites - I just use their default and facebook. It's a great way to swap routes with friends). It also tracks pace, split times, and elevation gain. It also guestimates your calories burned (not sure how accurate that can be). You can also set it up for different types of workouts, such as running vs. biking. It also has audio queues that tell you verbally your pace and speed at certain intervals. That feature even integrates with your music player (even Pandora) on your phone by lowering the music a tad when the audio performance queue is played. Overall it seems to be a very feature rich application. Best part is the price - the thing is a free app.

The price is right.
If anyone knows of anything they like better I'm all ears though. I haven't tried them all.