Last week my cousin and I had a write-a-thon at Caribou. It was awesome. I highly suggest this if anyone is priveleged enough to have such a wonderful cousin and fellow writer as I do. First, it's helpful for me to have someone next to me who is also writing to keep me motivated and accountable. There were times I would rather have surfed the net or tweeted away the hours because I was working on a difficult scene. But because she was there, I pushed through it. (BTW, it especially helps if they can see your computer screen so they know if you're writing or not.)
Also, there were countless times when I needed a name for something, needed a synonym, or just an extra brain to pop out some ideas. We went back and forth asking for words, definitions, etc. "What's someone called who's in charge of a school but sounds more medieval-like than super-intendant?" (Provost is the word we ended up with for that one.)
And, of course, every now and then we ask each other for a metaphor for something. It's always tons of fun because at this point, we can either be serious or say something hilarious.