It looks like you've gotten plenty of good suggestions for more mainstream rock. I recommend Music Direct too--their prices and selection are pretty hard to beat.
There are also plenty of rock/punk/underground/independent record labels that regularly release new music on vinyl. I'd recommend checking out labels like Lookout! Records, Empty Records, Dischord Records, Sympathy For the Record Industry Records, etc. www.worldwidepunk.com is a good resource for web addresses for these an LOTs on other indi labels. Keep in mind that the music that falls under the umbrella of punk now is a lot more diverse than just the Sex Pistols. If you're feeling adventurous, there's plenty there to keep you busy.