Hey SilverTurtle, my chapter has used
http://www.chapterboard.com since 2008 and we love it. Our girls are on it every day and it's so much easier to organize chapter events (especially when girls forget to bring their printed calendars to meeting). You can RSVP to events too which is really cool, and post comments like what you're bringing, who needs a ride, etc. The iPhone app is killer (you get all your member's contact info in the app) and they also have free group text messaging which we use a lot. We don't collect dues with them (national contract like ZTA) but my boyfriend's chapter uses them for dues and they really like it. He also told me that you can pay your dues thru the iPhone app which I thought was pretty cool.
I think the best part is that it's free (but I think you pay for dues). Hope that helps! Good luck in your search!