OK...so you'll actually have to get a BOOK, a real, paperback book...but trust me, it's worth it.
It's called Checking on Culture
, by Lee Killough, and it is an amazing (yet concise) worldbuilding guide for sci-fi and ANY type of writing you could do, that helps you get a handle on your world so that it's internally consistent and you know what may be different from our world. It has a "checklist" of areas to go through, that are an awesome help for brainstorming.
It's sold by a small press--Yard Dog Press--in Arkansas, but don't let that fool you. It's GOOD.