DeskPRO is a great inexpensive option - granted, it's not free, but it is well worth the investment. (Depending upon the package which you select, you may or may not have full access to the source code, however, the interface is easy to customize with the built-in tools provided)
Check out their free demo and see how it stacks up against other options (and try e-mailing the DeskPRO support department - I have found their support to be excellent).