If you want to know things like history, what they stand for, etc., I'd suggest going to their national websites. Every NPC sorority has one and it's generally
www.theirwholename.org (although Tri-Delt is
www.tridelta.org).
That won't tell you what the local girls are actually like, but it will give you some idea of where they come from (and it'll give you a leg up on remembering chapter names come rush!). If you can visit campus, I'd suggest doing so, too. Even though school is out you can at least drive around and check out the campus and Greek houses and whatnot.