Short of fully creating a new profile, there is no easy way to create a completely different desktop experience using most desktop environments. If you use KDE, you can easily create one setup for work, and one setup for personal use.
This is how I set up two desktop environments on my Ubuntu 10.10 computer (with KDE 4.5.1), using Activities.
The default KDE setup on my computer is nice, but I also want something a bit more customised for my work needs.
To start, click on the "cashew" on the top right-hand side of screen, and select "Activities".
This will bring up a bar at the bottom of the screen with all currently created activities in it. Click on "New Activity...", off to the right, and select the type of Activity you want; I chose "Folder View" (so that I could have some icons on the desktop). Customise the new activity to your hearts desire, I decided on a rather cluttered look to this one; I added multiple new widgets and changed the background. Regrettably you can't yet change the panel(s) between activities.
I now have two Activities that I can use, the default, and my new one for work. Using Activities it would be easy for me to create more for social networks, comics and use only on Tuesdays.
Quick note: While KDE is mainly used on *nix systems, it is also being tested on Windows and Mac OSX.