Your price range is just a bit short of where it gets interesting.
The Canon HV20 with its 24p capability would definitely be great. Only editing the 24p footage is troublesome, as iMovie doesn't do it, and Final Cut Express doesn't do it, either. There is some way to edit 24p footage in 60i on Final Cut Express, but I have not done it myself. 24p editing is, unfortunately, much cheaper for the dark side, ah... the PC 90% of the world. The problem is, that there is a complex pulldown involved, where progressive frames are recorded in interlaced mode on tape.
But still, the HD footage of the HV20 is great, and even if you want to watch it in SD, the HD footage, downconverted so SD, beats any native SD camcorder.
If you really want to stay within your 500$ limit, you can only buy an SD camcorder. Which is no problem, as there are some good ones.
If you can find a refurbished Panasonic gs500, a 3CCD camcorder with large CCDs (and better low light sensitivity), that would be interesting. Or maybe you can get a new unit of this discontinued model. The gs320 has smaller chips, but is a decent 3CCD camcorder, and inexpensive.