A lot of people have been asking me for something like this I know that this is not a new issue over the internet or even among photographers communities but since you asked for it then it is an article about this.
I know David Hobby talked about it last year on his Strobist page but is never too much to mention it again.
The guy who created this really useful tool as multi-layer .psd file for all pPhotoshop (Mac and Win) is Kevin Kertz, unfortunately after one year since I downloaded v1.1 he still haven't updated it with new lighting gear... maybe we should mail him to get an update version ;)
At least it still have some good tools for your photo setup projects.
There is also another version similar to this one that you can use almost anywhere and without Photoshop since this is an online version of almost the same product created in Flash named Lighting Studio.
This one is not a so visual complete version as the .psd one but it's also very useful for some on site or quick setup remembrance build when Photoshop is not in hand.
I think it's pretty good for a Flash web one, oh well at least you got a good looking model to play with :)
Here are the links for each one:
LightSetup .psd zip file
SDGPhoto Lighting Studio
Photographer Maurice Mc Duff have some great examples of what you can do with this.
Enjoy them and have a great weekend.