I'm pretty new to Brewing but morebeer.com has been a good online resource for me. I am really lucky that I also live within driving distance of their Concord California storefront. That place is the Toys R Us of brewing.
I also use a local store called Brew and Wine Makers of America ( http://www.beerandwinemakers.com/ ). The owner Rich has been very helpful in getting me started in brewing. He has put together my first two recipes. The first one I royally screwed up but am still holding hope(it's only been in the bottle 2 weeks) and the second is in the Primary right now. It's looking really good(probably because I followed directions!).
I'm sure others will chime in with this but I like Austin Home Brew quite a bit. Here
Shipping is flat rate, even if you're getting 100lbs of stuff and service was pretty quick. I happen to be fortunate enough to live in the same state and from the time UPS picked up the package to the time I got it was about 1 day.