Audio is often overlooked in most web video, which is unfortunate because poor audio is perhaps the number one reason people stop watching a video. Dropped frames are forgivable, but if your audio is good, poor video is less noticeable.
Up until recently, getting good audio from a sub-$500 camera was not an option. Then Kodak came out with their Zi8 at about $180 which has an audio-in jack. However, a quality microphone will cost you $200 more.
Samson, the company that brought us the Zoom H2 audio recorder with great sound quality, now have an audio recorder with a HD video camera inside. The Q3HD Handy Video Recorder. This little gadget features 1080p capabilities (at 30 frames per second) and 720p at 30 or 60 frames per second, a 2.4-inch color LCD, NTSC/PAL TV and HDMI outputs, and a USB 2.0 plug. The best feature, of course, is the built-in stereo microphones, so the camera should provide much better audio than your average camera.
I've seen it offered at $299, but I'd have to see a sample before making a purchase. Will the field of view be too narrow?