Three days ago I installed the xgl server on my workstation. It's working fantastic. I really like all the glowing, shining, blinking and wobbling windows. At first I thought all the grafical enhancements are just nice gimmicks. But after using this stuff for about 2 days I realized that xgl changes the way I am working on my pc. Now I can not even think of not using the transparency features, to have the php documentation in the background while I am coding.
You should really try this out. It's some kind of a new experience. And it is even working in a multi-monitor environment, like the one I am using.
If your gfx-card is supported, installing isn't that hard. I will give you some tips how to do this on gentoo linux.
After you have emerged all the packages for Xgl you should take a look at the compiz forums. There you will find icons, themes and usefull tips about your new window manager compiz.
Because I wanted to have a "really" transparent console, I needed a way to start applications with a predefined transparency value. This is really simple. Just emerge the xwininfo , xprop and the transset package. After all these applications are installed you can use a tiny script I have written to do exactly what you want. See the end of this entry for the download link.