Well that depends, wuzupmike. I'd look first at what you know best. Do you have a hobby that you can write about? Maybe an instructional for one aspect of your hobby? How about food? Is there a recipe that only YOU know how to make, and can you share that with the community?
Personally, I think anything is a good topic. I read all sorts of weird and wonderful things on Hubpages as long as the author sounds like they know what they're talking about.