#1, go here -
http://www.t-shirtforums.com
Almost any topic you may wish to learn about, from color separation to suppliers , you can find out there.
How to start a clothing line from scratch - Lots of articles
http://www.dobizo.com/
A great, but expensive wholesaler of some original and popular styles, they do custom clothing, hang tags, private labeling, all that -
http://www.alternativeapparel.com/
http://americanapparel.net/
If your looking for small volume purchases of simple blanks, check out Tara at -
http://www.a2zexchange.com/
http://www.myspace.com/a2zexchange
She's always been good to me, and doesn't make me buy in lots of same color, same size, etc. She can usually get any style.
People are still loving the distressed look, retro, and distressed or original texts. At least the kids in Highschool, my market are.
Hopes this helps, especially I know you'll find the first link, T-shirt forums to be helpful, good luck!