As previously stated, check out Vacation Rentals by Owner. You can also google vacation rentals Orlando and you'll come up with several other sites.
Not meaning to scare you, but do your homework on the property before renting. There are LOTS of condo associations in serious trouble so when reviewing trip reports, make sure they are fairly recent. I toured one association which used to be 4+ stars, but now can't afford to keep up with landscaping or pool care. There are even a few realtors who specialize in short term rentals.
My personal experiences have been good to great at:
Vistana
Orange Lakes
Vacation Village at Parkway
As mentioned, there are some great vacation homes too. You can get a very large home with a pool and hottub for about the same price as a condo. We're planning a HUGE 2013 trip (50-60 people) and those that aren't staying onsite are planning on renting homes. There are even some vacation homes that have great community pools/lazy rivers.