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.
Quick note: While KDE is mainly used on *nix systems, it is also being tested on Windows and Mac OSX.