I've got a Danby 6,000 BTU unit and it works pretty well. The convenience is the kicker though. You can move it around from your living room to your bedroom easily and get nice cool air. Portable A/C units don't cost 1500 bucks. Unless you get the top-o-the-line ones with gold leafing or what.
My model retails at your local Home Depot for around 600 bucks or so give or take a few dollars. Haven't checked the retail price lately but that's ballpark.
It has multiple modes from cooling to dehumidifying to fan to heat. 4 in one. We're very glad to have bought it. The price of admission is relatively high but it's worth it. Some names for portable A/C units include Danby, Toyotomi, I think Carrier has some and others.
I haven't checked out WombatWoman's link but it's probably the A/C thread awhile back.
You can buy port A/C units at any Home Depot whatever.
If your needs are simple and always in the same area then you might consider getting a window-shaker unit as they are cheaper per BTU and more cost effective. They also have high BTU ratings for greater output. But the caveats are that they don't move, you have to do some fancy install here and there although it's not hard, the unit will stick out your window and it will be a security risk and a window unit may not even be an option if you are renting since it's invasive with regards to setup.