Glad to see someone listed Park Tools. Here are a few links I found useful, particularly if you are looking for cheap items or do-it-yourself stuff.

Everything you wanted to know about DIY bike lights:
http://nordicgroup.us/s78/

Making bags and such for your bike:
http://www.mile43.com/peterson/BarBag.html
http://www.mile43.com/peterson/Kents_Tailbox.html
http://www.kenkifer.com/bikepages/touring/bags.htm

For female commuters and some good links to more DIY stuff:
http://www.girlbike.com/doityourself.html

Good general advice and amusing stories:
http://www.commuterdude.com/

Cheap, obnoxiously hi-viz polyester t-shirts:
http://www.alertshirt.com/peap.html

If you need to commute with a lot of stuff, here's a DIY trailer:
http://www.motherearthnews.com/libra...icycle_Trailer