When I run, which is never as often as I'd like it to be, I like to track my progress both during and after my activity. I like to share my runs with friends so they can see I don't ONLY sit on my butt all day, and besides, it's encouraging to see people commenting with "way to go!" or similar sentiments. The RunKeeper app for iPhone (also available for Android or Windows Phone 7) helps me to do all of these things, and much more. It's a free app, and it uses the GPS feature of your phone to track your runs. It syncs with the RunKeeper website where you can analyze your runs, view maps, and much more. There's no way I can cover all the features, but I'll tell you the ones I use the most.
1) Coaching: you can set RunKeeper up with coaching programs. Trying the Couch to 5K? You can program in each run before you do it, and it will tell you when your run/walk intervals are. Looking to maintain a certain pace? Set Runkeeper up with your target pace, and how often you want to be reminded, then it will tell you your average pace, current pace, and how far above/below your target you are. If you are doing speed training, you can set the app up with a coaching plan to tell you when to run fast versus when to recover. You can set up these intervals by time or by distance, which will likely help satisfy just about any training program out there. You can even tack on a warmup/cooldown to your workout.
2) Music: if you already run with your phone, chances are, you listen to music during your run. RunKeeper lets you pick a playlist from your phone to play while you are working out. The music fades a bit quieter when RunKeeper is telling you stuff (like RUN FASTER, BEE-OTCH! YOU CAN DO IT! OK, well it doesn't actually say that in so many words...but you get the idea)
3) Post to Facebook: you can post your runs to Facebook and make them visible to everyone, just your "street team" (friends using RunKeeper that you've selected & added through RunKeeper), or just you. You can make all the run information public, or maybe not the maps if you don't really want people to know where you are running.
4) Analyze your runs: On the RunKeeper website you can check out the details of your run, the elevations of different segments and how that affected your pace. It sends you encouraging emails every time you break a "record" (such as, Most Distance logged in a month, or others like that). There is a RunKeeper Elite version (you have to pay for it) that gives you access to extra reports. I don't have it so I can't comment on it.
5) Live Tracking: OK, so since this is an Elite only feature, it's not one I use, but on certain occasions, you might want to be able to turn on live tracking. This basically posts your run online while it is happening. This is a nice feature if you're running in a race and want your family/friends to track your progress (or to give them a heads up when you're near the finish line, so they can make a point of seeing you cross the finish...). It could also be helpful if you are trail running, or going out for a solo run and just want someone else to know where you are.
If you are a runner (or walker, jogger, cyclist...) who would like to know just a bit more about each workout, you may enjoy using RunKeeper like I do. Go check it out over at http://runkeeper.com/home. If you already use it, let me know in the comments what your favourite thing about it is!