Big orders and ingredient kits- http://www.midwestsupplies.com/
Small orders (they've got good shipping rates)- http://www.austinhomebrew.com/
How-to's are all over Youtube. I used to have a few helpful links saved on my computer, but it crapped out on me. I did a whole lot of reading to try and understand everything about the process, but it's fairly straightforward if you don't want to start tweaking recipes, or creating your own from scratch.
I'd recommend watching some how-to videos on Youtube (I recommend craigtube
as a good starter for extract brewing). You can do full extract brews like he does, or you can go and pick up a partial mash batch like I did. If you buy a partial mash kit, it will come with instructions, and you can learn the basic process for brewing from that.
And if you've got any questions, we've got the Home Brewer's thread in OSST, and there are homebrewing forums all over the internet. There's an entire culture dedicated to homebrewing, and a quick google search should bring up answers to any questions you might have.