I've been in contact with a number of frats over the years. There is a wide range... Many aren't much more than a "boys only clubhouse," but from time to time, I've found a few that really seem worth joining (great group of people, solid fundraising for worthy charities, fantastic non-drinking extracurricular activities, etc.).
I really recommend doing your research before even considering joining one. Many could care less about you... they just need warm bodies, membership dues and someone to fetch them a beer.