Here is one of the songs I've been making with the excellent Wikiloops community. In case you don't know how that site works, goes like this: someone posts a track, and then you put something on top of it and post it, then someone else adds something more...
In this case I added vocals + a guitar solo to an already very mature and well crafted song. Everything in this site has to be done on the go; as with speed dating, that's all the fun of it; things must run snappy... and that's one of the things I like best about it. It takes a lot of effort out of the process, it reminds you that it's gotta be FUN!, and gives you the constant reinforcement of stuff getting through the door every other day.
This one is perhaps the most elaborated of my collaborations there up to date, and took me ~7 days in total. To provide a contrast, some of my solo stuff can take me easily x50 times that! (Fortunately, things are changing on that regard, I think.)
Other thing that I enjoy about this site is that it forces you to "go places", to try things you wouldn't on your own; I would never have thought I would sing a song in the style of this one in a million years. I have other, for example, in which I found myself trying to emulate AC/DC's Brian Johnson style (although a few octaves below)...
I have a guitar and I'm gonna use it