We have an MSN group that is Chi O only, but you have to apply for membership and then you have to dig through the threads (there's no search function), so I saved you the trouble and have copy and pasted some ideas here.
I personally like a system of gaining a certain amount of points by the end of the year to be able to attend formal. Or perhaps not getting points results in a work fine (cleaning the yard before recruitment or Homecoming, etc.). I think monetary fines aren't a good idea for this. Also, I'm not so sure that winning a "prize" is enough incentive. Expecially if you girls are anything like we were when I was there! We wouldn't care about a prize...formal, that's another story!
Maybe you can read through this with your Eboard and pick and choose the ideas you like to make your own system. An interesting note someone mentioned, sometimes girls going through recruitment get turned off by the idea of a points system. Hmmm....
Warning - this is long!!!
1)assign a pre-determined number of points to each event. If you attend a manditory event you don't get points, but if you have an unexcused absence, you lose points. You get points for optional events. You must have a minimum number of points by the end of the quarter or you get a personnel meeting or something. There is either a prize for the person with the most points or there is a prize for all the people who got above a certain level of points.
2)"14 Pearls." At the beginning of the semester, make pearl sheets that resemble our badge. Make up a list of Pearl Events (sisterhood events, study hours, community service events, etc.) that the sisters would go to and earn "pearls." They would have to earn 14 by the end of the semester. Remind sisters at the beginning of the month which events were worth pearls, and add to the list if new events are planned.
If an event was especially important, make the event worth 2 pearls. I also made some mandatory events worth pearls, and perfect attendance to the meetings was also worth a pearl.Every other Sunday or so to attach round, white stickers (from any office supplies store) to the sheet. At the end of the semester, put everyone's name who had earned the 14 pearls into a hat, and they received a chapter badge guard. The first guard was bought by the advisors, and after that it was supposed to be put into the GKA's budget. Sisters really enjoyed seeing the sheets in their folders and comparing it to other sisters.
3)Teams
Divided the chapter into two teams, Cardinal and Straw. For all of those little events that we needed sisters to attend on campus (Greek Speaks, other chapters' philanthropies, etc.) we would assign it to one team. If you were on that team, you were required to go, or send a replacement from the other team. It started out great, but quickly deteriorated when it was harder to find a replacement.
4) More "points"
When our Nt'l Cons. came, she liked the idea of changing it so that the point system wasn't so basic (ie - 1 pt. for every activity). Instead we changed our system to a format where certain activities were more significant that others, like Community Service and C & P Dev. activities were worth 3 pt's rather than the usual 1 pt. that socials/mixers are worth. (The ladies will allllways attend an event with bells on if there's men, as we know!

...) Soo...that helped a bit - it was an incentive for some to take part in things they usually steer clear of.