I just found a terrfic brainstorming site that I'm becoming quickly addicted to. It's called BrainReactions and it's a community of people who post questions like "What should newspapers be doing if they want to survive?" and "How can I communicate better to a large audience?" and then wait for responses from other users.
The addictive part of it is that you can scan through the list of questions and quickly post an idea in a matter of seconds. There is a truly diverse bunch of ideas to brainstorm about so you're bound to have something you can expound on. Posting your own question is just as easy.
While traditional group brainstorming is a mixed bag that's usually not worth the effort, BrainReactions is low maintenance and quick. If you don't get any good ideas from the community, it's not like you had to book a conference room, buy a bunch of doughnuts and spend hours getting nowhere.
BrainReactions.net Online Brainstorming and Idea Management Software - Open Brainstorms