Linux tips
ucanvcam should work out of the box on linux, in the sense that you can read images from a webcam and apply effects.However, in order to output the result as a "virtual camera" that something like skype can read from, you need the vloopback module. And video support specifically in skype on linux currently has some limitations, so you may need the common "gstfakevideo" workaround to make it happy.
vloopback module
The vloopback module lets you create a virtual video4linux device.See http://www.lavrsen.dk/twiki/bin/view/Motion/VideoFourLinuxLoopbackDevice
ucanvcam is tested against vloopback-1.1 (look for vloopback-1.1.tar.gz or newer). Download, install, and "modprobe" the vloopback device.
When you restart ucanvcam, you should now have two /dev/videoN listings that do not correspond to any physical hardware that you possess. One of these (the lower number) is where ucanvcam should output to, and the other is where other applications can read the transform video stream from.
skype support
Hopefully by the time you read this skype's video support on linux will have improved. In the meantime you may need to download gstfakevideo - See http://code.google.com/p/gstfakevideo/Run a command like the following:
gstfakevideo v4lsrc device=/dev/video1 ! ffmpegcolorspace