Also-- there are often fraternities and sororities (both single sex and co-ed) that are specific interest, in addition to the NPC ones. If the larger three don't feel like a good "fit" for your lifestyle or are too expensive for you to join, but you're still interested in a fraternity or sorority, do give the smaller organizations a try. They usually don't have the social impact of the larger ones, but the friendship bonds are still as strong. Since they're usually not welcome at the formal Greek rush events, they don't get noticed as well-- and every new member can be a blessing.
~ Mel.