PA Speakers for Parties

I am brand new to this whole scene. I am in a fraternity and got elected to run certain aspects of our parties. What we need are PA speakers (our old ones broke) They need to be self powered, I am not really sure what exactly a decent setup would be but parties are generally in a huge room with close to 100+ people. We had two older speakers that managed for a few years before biting the bullet. Anyone have any leads they can give me or tips, brand new to this whole thing.
First question, what's your budget?
Second, what equipment will they be used with?
There's more questions but, answer these two and folks will have a little better idea of what to recommend.
One point is whatever speakers you buy, the volume controls should be modified so they never can go to 100% volume. make the volume coontrol lock/top out at 70% of full volume. Then they will be way less likely to ever just be blown up at some future drunken brawl called a party.
Also, bigger is better for SPLs.. Small speakers just have to work way harder to cover a big crowded space.
You should go ask DJ and Rave sites to know what sort of equipment to buy.
Audiophiles would not know.
Thanks for the input, I literally have no equipment, its mostly to play ipods with playlists and such. My budget is around $300.
I think your budget is unrealistic.. Big room ( get the exact dimensions) lots of people.. playing dance music.. you're gonna need some real stuff.. Google is your friend, but here's a link to get you started.. might even want to give them a call...
This might work for
Go away.
Lots of little active nearfield monitors in that price range (Behringer, M-audio, KRK) but they aren't for party level SPL's. More realistically, over $2000 (bigger Mackies and JBLPro). Then, you have to convert to XLR.

Cheaper to pick up some old Advents, or whatever, and a used receiver in a yard sale or your local craplist.
Check out the Behringer Eurolive series. You might have to raise your budget to the $400-500 area.
JBL Eon series. Built like a brick sh**house, and sound pretty damn good to boot. They are nearly indestructible, unless you do something really foolish.

That said, be nice to your neighbors and don't torture them with throbbing bass until 2am. Remember, someday you'll be living somewhere, working an actual job and needing to sleep. Karma can be very cruel.
go to a local pro sound shop.
With average tuition coming in at $25k/yr. you need to get more funding. Assess each member $500. Get something sweet that will put you guys over the top when it comes to the hottest raves in town.

I don't think this is the right place to look. This is more home audio from simple to extreme but people are looking more for more high quality from a listening spot than filling a huge room with ass grabbing vibes.
I agree that $300 will just not no no...but a grand might get you close. I am a veteran live sound pro...I sue me! Now that that's out of the way I can easily suggest a pair of used Mackie SRM450s and any cheap used mixer (Behringer maybe). Pair 'em with an inexpensive used big powered (15" to 18") sub from, again, anybody, and it will take the heavy bass lifting off of the main speakers and allow your dubstep binge drinking party to get the cops called every time! Use the failed careers of musician wannabes as your key to this thing...bands sell good stuff cheap all the time.