For the under $500 range, I would think the two to look at would be the Sony HDR-CX260V and the Panasonic HD-V700. Both offer entry into the ability to capture full 1080p at up to 60 frames/second. These start around $350
The Sony HDR-CX260V can be had for $369 at Amazon
right now (need to add to cart to see price) - which seems to be a pretty good price given the cam comes with 16GB internal memory. Note that the HDR-PJ260V that is currently $100 more is pretty much the same as the CX260V, except it adds a gimmicke projector function (not worht the extra $100, in my opinion)
The Panasonic HD-V700 can be had for $349
- but no internal memory. For 16GB internal memroy you need to go up to the HD-V700M (which costs $529 - not worth the extra $180 for 16GB of memory in my opinion).
I don't think you can go too wrong with either. I don't have any experience using either of these cams personally, but here's a thread from AVSforum
where someone conjectures that the Panasonic's slightly larger sensor may be a bit better for lower light.
Edit: If you can afford to go above the $500 mark, the HC-X900M
(with 3 CCD censors instead of 1 for better color and detail compared to above cams and built in 32GB memory) for $648 seems a pretty good deal too. Here's the one
without the internal memory for $599