I recently signed up to run my first Chicago Marathon 5K in September 2012, and hopefully will be doing others before that. It's so far away, but I'm already nervous! I can run 3 miles now, but it's still tough. I figure by then I will be able to do the whole thing, no problem.
It's always been a personal goal of mine and I finally sucked it up and paid the $25 registration fee to run.
Another one I want to run in is the 'Run for your Lives' race in Indianpolis in June. It's a 5k and obstacle course that you run through, all while being chased by Zombies. I can't imagine a funner way to run a race, and obviously it would give you more insentive to finish when you're running from something instead of for something I suppose.