First off,
Partying is always going to be a tough one to top, nothing beats getting drunk with your brothers. I'm sure they can just stand around for hours playing beer pong just like us. But if you want to be more than just a drinking club and really get to the cool stuff fraternities are known for, drop the bottle and pick up a pen....
First is athletics, if you don't have an elected athletic chairman working with the social chairman, better get one fast, and make sure he's motivated too. We have a blast playing big brother/little brother football, or you can modify it for a pledge activity. Also, find out if your greek life assoc. has any greek olypmpics, competitions with other houses, etc. Not only does it build greek unity, but you get to have fun too.
Next, time for some community service. The mere sound of it makes my brothers eyes roll and an unknown birthday pop up for that day. But the trick to it is to really find something useful and interesting when planning one of these. If you really want to get crafty, do it in conjunction with another sorority. This creates two side effects:
1. Guys will show up to impress the sorority girls on how much they care about community service, if its working at a soup kitchen, holding a blood drive, or doing an adopt a highway cleanup or a local project like that.
2. You guys improve your rep, possibly get an article in the school paper (pro-greek articles are usually printed in the 3rd to last page in the left bottom corner with your house letters mispelled

, time flies by faster when your enjoying yourselves with the presence of good company.
Community service is always the hardest one to get people motivated to do, so start with something simple and short, move up once you have good solid participation.
Now if it's all about partying, and you want to get rid of the alcohol for one night. You might call me crazy but try a joint mixer with a good theme as well as a distraction to the awkwardness besides alcohol. For example, 70's theme night kareoke. You got the 70's get up going on, and then you have the kareoke guy. Most guys won't go for it, but if you can get it started, I guarantee it will hit a home run for laughs and fun.
If you guys have a lot of time and gas, maybe a good ol' roadtrip is in order. Make sure you do this outside a pledge period, they just never understand and someone always gets the house in trouble.
The last idea that I can think of off the top of my head is a little non-par. Plan a prank, heh, well something fun and not damaging to another greek house. I remember when a fraternity chapter came down from another school and conducted a panty-raid at one of the sorority houses. I'm sure if we tried a stunt like that then the police would of showed up. But honestly, even if they did, what's the worst that could happen??? Well, maybe I shouldn't say that cause knowing me, the worst would happen... Anyways, nothing beats being creative so think up something original for a prank and as long as it's safe, and no one gets arrested, it'll be the topic for discussion for weeks to come. Or maybe just the following night when you break out the keg again. Anyways, I think I put as much as I can think of right now.
Goodluck!!
- RUgreek