What a fun and interesting thread!
It's really hard for me to think back to when I was 18, so my choices are influenced by women I've known and what I've researched. Here they are, in no particular order:
Kappa Kappa Gamma - I love their colors (similar to ours!), love their symbols (especially their badge), and I like that fact that, as someone else pointed out, our founding members considered joining them before starting AXiD.
Kappa Delta - All of the KD's I've known have been so classy and are just the nicest and most helpful ladies. I love all of the organizations they're involved with, and green is my favorite color
Zeta Tau Alpha - Out of all the philanthropies, I think I like theirs the best. I keep learning of more and more people I know who are affected by it. And I love the crown.
Theta Phi Alpha - I have no idea why, but for some reason I really strongly identify with this sorority. I just get a good feeling about them - even though I have never met one and we didn't have a chapter at my alma mater. And I just love their creed - so beautiful.