What is a good place to learn more about the commander format?

I haven't played since 4th edition and it seems that what is played most these days is the commander format (at least in my area).

My approach to deck building has always been very combo oriented, but that seems impossible in a 100 card singleton format. I'm having a hard time wrapping my head around what a commander deck is supposed to look like and how you're supposed to build one. You really can't build around any one card since you just get one single copy...so how does it work?!