Whilst I was at GDC I picked up a free Creators Club membership at the XNA sessions. I think it is for four months, but you may be lucky. Anyhoo, I'll give it to the the person who comes up with the silliest game idea in the next couple of days. My decision is final (I consider myself an expert in silliness).
Remember that if you are a student on a course of study you can get a Creators Club membership for free via DreamSpark, but for anyone else out there, this might save a bit of cash. Put your idea as a comment on this post.