WARD  Compatibility Note: iUSBCam is no longer supported in Mac OS X 10.6 (Snow Leopard).

source: http://www.ecamm.com/mac/iusbcam/  
(Version 2.2.5)

SNOWWHITESICKETTE  I am very happy with iUSBCam. It works as advertised, with a Hue Clique USB webcam and 10.4.11. The developer is helpful and prompt responding to questions. I had asked about the licensing, and the developer informed me that my license is good for all of my personal Macs, which makes the low price even better. The trial period is one week, which is plenty of time to determine if it will work.

A driver must also be installed for the USB camera to work. I got mine from the webcam manufacturer's website- the most recent driver instead of the outdated one that came with the CD. If your camera manufacturer doesn't have a Mac OS X driver, check out Macam, a free USB webcam driver that is available here at MacUpdate.

For some reason, the feature that IMO makes iUSBCam a necessity, is not even mentioned in the description above. It enables older Macs that don't meet the requirements set by Apple to broadcast video in iChat and other IM programs. I installed it on a 400MHz G3 iMac and a 466MHz iBook SE, and it works perfectly. Also enables an external iSight to work on older Macs that fall under the requirements. Prior to iUSBCam, the iSight would power itself off after showing a few seconds of video- enough to know that the computer was not the problem. Because of iUSBCam, I can use my USB webcam in iChat, or my FireWire iSight on all of my Macs. Fantastic!  
(Version 2.2.5)

OHGOOD  iUSBCam 2.2.4 seems to work with Leopard 10.5.2 and iChat (current) but usability is very poor. THere are problems with the application apparently, as this is being written to syslog 10-20 times a second: 3/19/08 8:20:43 AM iChat[803] *** Break on _NSLockError() to debug.

Which means the ahrddrive and cpu are going like mad.

Working and usable are two different things. :)  
(Version 2.2.4)

DONKEYOTAY  I have a Logitech Quickcam with an inbuilt microphone, but cannot get the audio to work. Beautiful pictures though. Any help?  
(Version 2.2.1)

CLOUDNINER  This program is a ten! I have a 24 inch iMac with the built in camera. I really like the ability to use a USB web cam as it gives me the ability to sit and relax instead of sitting fixed in front of the iMac. Gladly bought the program minutes after using it.  
(Version 2.1)

MACGURUTECH  Outstanding software makes usb cameras finally useful on any OS X Mac and very nice interface can easily compare with Apple's own cameras.  
(Version 2.1)

RIOTGURRRL  It doesn't work with the Eye Toy 3 camera (usb; sony; SCEH-0004 (??)) which is an usb camera can sombody HELP me?  
(Version 2.0.6)

ANONYMOUS  Works great on Tiger and Powerbook 667DVI  
(Version 2.0.6)

ANONYMOUS  How come I cant get more then two people in a video chat(me and another person)?Is it because I havent registered yet?Great software though,I dont know why apple didnt include support for usb cameras.If the camera works in quicktime I dont understant why it wouldent work in ichat(probably because they want people to buy the isight).Very usefull software,alot cheaper then a 150 dollar isight.  
(Version 2.0.6)

RUTGER  Version 2.0.3 works perfectly on tiger with macam and the Philips USB ToUcam on my 1GHz G4 PB!  
(Version 2.0.3)