This thread contains a wealth of information to get you started, or at the very least enough info to make more informed decisions.
This may be blasphemous, but Ars recently put out a great DIY guide for building a router.
In my personal opinion, while DIY Routers are often more "powerful" than those offered retail, the extra power is often wasted or not fully used, at least in majority of consumer applications. It's better to get a decent retail router and re-flash the firmware with something like Tomato or DD-WRT. You'll get the same level of control over your network and a near identical feature set in a drastically reduced amount of time.
EDIT:
We put out this great primer on wireless networking. If you want to get into the nitty-gritty on what makes a great wireless network this is the guide for you.