going for standalone cam with built in DVR or going for FPV type setup also makes difference in choice some times. You might want to look at RC switch for cams too to switch on and off your cam remotely
I know another couple other popular options are the smaller types like the KX171 and KX191 I also just saw a nice HD helmet cam get used dont recall the name of it but it may be just out or just around your price range. Also the FlyCamOne 2 gets used alot but the FlyCamOne 3 I do believe has more movement options with the lens (pan/tilt) than the FlyCamOne 2 model.
I'm using the "gumstick" video camcorder since it can fit easily into the EasyStar canopy - just cut a rectangular hole that is on the canopy downslope center and you end up not seeing the nose (unless you really want to). The camcorder can be found for about $35 with 2 gb of MicroSD - which gives maybe 40 min of 640x480 (15 or 30 fps - not really sure). The EasyStar doesn't seem to create vibration to the camera mounted like this - no wavy motion. It is only 18g in weight - really easy to use. Some examples of it (remember that the original AVI has more detail) are on Vimeo. See these: http://vimeo.com/8766337 http://vimeo.com/8766442
I would like it to focus a little better in the distance - so far I simulate that by using the "sharpen" filter in Vdub.