I am not an expert on webcams.
high-resolution
forget the bloated MP values quoted for picture taking - go with the optical resolution. software interpolation just uses up more disk space and doesn't give you any better picture than the effective/optical resolution. see my MP calculator (4:3).
Logitech C910 HD webcam
3MP HP Elite Autofocus Webcam (AU927AA#ABA), available from hp $100
(2000x1500 [4:3] or 2309x1299 [16:9] I am not sure which).
autofocus, USB 2.0.
HD video wuality.
Software: ArcSoft VideoImpression, ArcSoft Magic-i, ArcSoft WebCam.
slideable privacy cover.
up to 30frames/sec on broadband.
computer security motion detection "snapshot" software.
button for bring up your favorite IM program.
works with AIM, Windows Live Messenger, Skype, and Yahoo Messenger.
snapshot software interpolation up to 19MP (but I don't care for that)
Logitech QuickCam Pro 9000 2.0MP Effective Pixels USB Interface WebCam - Retail, available from newegg $85+9
1600 x 1200 "HD quality" or 960 x 720 "HD" Video (these are not HD resolutions - see wikipedia). 4:3. Built-in microphone with RightSound Technology Ultra-wide. Autofocus. Mac version available for $130.
Microsoft LifeCam VX-7000 2.0 MP Effective Pixels USB Interface WebCam - Retail, available from newegg $70+9
approx. 1600 x 1200. 4:3. Built-in microphone with RightSound Technology Ultra-wide. Autofocus. Optimized for Windows Live Messenger. Auto-adjustment for low-light conditions. Universal attachment base.
Philips Webcam 1.3MP SPC1300NC/27, available from philips
approx. 1317x987. (close to HD, but not quite) 90frames/sec.
Low-resolution
ABS MegaCam 312M 1280x1024 MAX Resolution MegaPixel, Day/Night Wireless & RJ45 Network Camera with 2-way Audio, Indoor - Retail , available from newegg $140
This one is meant for security. (6)IR Night Illumination. Wired or 802.11b/g networking. Free software application to view/record up to 16 cameras simultaneously. built-in mic, 2-way voice communication. Voice alert when motion is triggered. Intelligent motion detection with 4 zones detection window. Remote view/monitor with 3G cell phone (3G Cell Phone and service is required). Up to 10 users simultaneously with different resolution. Wall mount, desk/ceiling mount, tripod mount. Search your IP camera on Internet with DIPS(Dynamic IP Service).