As most of my site visitors can tell, I'm a big fan of eBay when it comes to band shirts. Flat out, there is no place else where you can find the variety of shirts that you'll find on eBay. This is mostly due to great sellers and eBay stores that go the distance to track down these rare gems and post them for sale. Its those eBay stores where I usually find great shirts to add to my collection. Most of the time I'm not even looking for them. Its when your browsing a store with hundreds of random t-shirts that you find the one that got away years ago.
Here is another great store with over 200 concert and vintage shirts for your browsing pleasure, Stray's Place. What I like about this store is their large selection shirts in the $20 -$30 range, a reasonable price for most fans. They also have a bunch of cool listings outside of the band shirt niche; I especially like the Hawaiian shirts.
I'd like to give a special thank you to Stray's Place for their contribution to Band Shirt Archive. They were kind enough to provide me with high quality images of ALL the band shirts they've listed over the years. I'm talking hundreds of shirts! Look for those to start being posted in the archive soon.