I was talking with some software developers over a great dinner last night and we got on a favorite topic, collaboration. I brought up one of my favorite tools, SubEthaEdit ($35 from www.codingmonkeys.de). You can collaborate on one open document across your network. It's also Apple Rendezvous (aka Bonjour under OS 10.4)-enabled, so it's easy for other Mac users to join in. Nice features such as color-coding for each user and time stamping make this a flexible tool. If you need some group-think without the use of a projector, this is a perfect tool.
For more on great shareware, see this useful article.