Looking for USB web cam suggestions

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I’m looking for suggestions for a good USB webcam.  My criteria:

  1. USB 2.0
  2. Good framerate.
  3. Very portable as it will be going with me on trips, etc.
  4. BUS powered is a must.
  5. Still picture capability nice, but not necessary.
  6. Embedded microphone nice, but not necessary.
  7. Face tracking software nice, but not necessary.

Any thoughts?