Panasonic or Sony
Check the camcorder reviews on
http://www.camcorderinfo.com and
http://www.cnet.com - I really doubt if you'd get a good camcorder with manual controls under $500, but these websites would give you an idea.
If you step up to around $750 or so you may even find some good 3 CCD camcorders (Panasonic has some good ones - GS150, GS250 etc.) with limited manual controls.
Focus on the lux rating for good low light performance - the lower, the better (with 7 or less being considered somewhat below average, and 2 or less considered average or slightly above average - note that these are my arbitrary classifications and I may be wrong on this aspect).
If you do find image stabilization, it'd be better to opt for optical image stabilization (OIS) instead of electronic image stabilization (EIS). Many camcorders in your budget would provide some kind of image stabilization (most likely EIS).
Avoid Canon like the plague - low light performance across all their models is very poor (more so in the lower price category).
Sony uses a touch screen interface on the consumer category of camcorders - so most of the adjustments or changes you make would have to be done by touching the LCD screen that you'd use for looking at the image as well - not a very good option since it makes on-the-fly adjustments impossible to do without shaking the camcorder. But if that's ok with you then you could look at the TRV or DCR-HC series from Sony - something like DCR-HC40 or DCR-HC90 (the latter is expensive).
Most camcorders would work with a Mac since they provide a FireWire interface to transfer videos (although the FireWire cable might be an additional purchase, with the best quality ones costing around $20 or more). Note that FireWire is the standard for video transfer - even though camcorders may also provide an USB port, you cannot transfer video through it (only still pictures). The only way to transfer movies into iMovie is through FireWire.
