Trendnet
Trendnet TV-IP100 works ok. http://x.x.x.x/video.cgi
Trendnet TV-IP300 : Just remember to turn 1.0 in ZM_HTTP_VERSION in the Options > Network tab. In the x.x.x.x/cgi-bin/video.jpg gives 352 x 240 jpg.
Trendnet TV-IP400 / TV-IP400W: These are cheap but fun Pan Tilt Zoom IP cameras and are now also supported by ZoneMinder.
New Driver and instructions for ZM 1.23.x : http://www.sfpeter.com/2008/07/31/new-trendnet-tv-ip400w-controller-for-zoneminder-123x/
Older Driver and instructions for 1.22.x: http://www.sfpeter.com/2007/08/14/controlling-the-trendnet-tv-ip400w-camera-with-zoneminder/ The above link is missing the "Move" tab when creating the control. You need to select "Can Move", "Can Move Diagonally" and "Can Move Relative".
TrendNet TV-IP301 This camera sends the wrong mime/type and is not compatible with ZoneMinder natively but can be made to work.