Here's a good link with plenty of ideas:
http://www.fundraising-ideas.org There are some really creative things on the DIY Fundraising page. Plus if you scroll down and click on fraternities it will give you a list of things that have worked for other fraternities.
As for what's worked in my chapter, when I was there, we did a topless car wash. No, it's not what you think.
We'd wash the bottom of the car for free (doors etc.) but we'd wash the top of the car for a donation. (I'd go no more than $5.) Obviously you would not want to do this during the middle of winter. After I graduated, the chapter did football parking. We'd have a couple people in a section of the stadium lot literally guide people to spots and collect money. We got a set amount of money per week, I think. You can also do this for basketball if the campus allows it. We also cleaned the stadium after home football games. It was a pain but we did make good money doing that.
Hope this helps!