I'm renting speakers for my wedding--rather than have a DJ, I'm going to get some college kid to play my MP3s. I don't know how big of speakers I need and I don't want to ask salespeople what they think because I don't want an exaggeration. There will be about 90 guests, and the space is a 3800 sq ft loft with high ceilings. We don't want to blow people away, just loud enough for dancing.
Cerwin Vega's are a good choice, but might be a bit expensive for a one time event. Check event planners in your area to see if they will rent their equipment.
Most places like that, that will rent their stuff, would probably have Peavy speakers. They are very common for PA's and mobile DJ systems.
You are going to have a choice though...and it's probably something that you implied but did not say. What are you going to run them with? Your home A/V receiver? Rent amps and sound board? You have options, but it's not as simple as just renting the speakers.
A pair of Rave II series KLH speakers might also do pretty well for your purposes and they are ~200 bucks a pair to keep. Jet brings up a good point about power too.