Open Tunings
I found an interesting site that has some good info on open tunings. There are some really good chord ideas. The rest of the site is a bit, um, weird. Anyways, check out the pages on Open D, Open G, Drop D and Low C. If you've never experimented with open tunings, particularly if you like to write your own songs, you should definately check this out. You'll get instant inspiration. Here's the link.