Starting a new single speed project... suggestions?
 

I'm starting a new project, and would like to refurbish a good single speed piece by piece. I ride a Shwinn World Sport 12 speed right now, so I don't have much time constraint when it comes to finishing it (as I have my solid, working commuter) and want this to be a good learning experience that I'll come out the other side with a great looking bike. Thing is, I'm stuck on the first stages of finding myself something to fix up!

I'm planning on working at a bike co-op just down the road from me once or twice a week, and can put in a good amount of time into each of the sessions. While they have loner bikes to work on at the shop, I'd really like to grab something great off Craigslist that is a hidden gem. Any suggestions on what to keep an eye out for? (as in, good brands, years... etc)

I'm looking for something unique, but also something that'll be user friendly once it's done. Ideas?

What do you want to do with the bike? Commuting? Racing? Distance riding? Beater to lock up outside the bar?