I recently discovered that
Lightzone is available in a Linux version. Though not as supported as the Windows version, this version is currently free. I have it running and will be testing it more thoroughly in the coming weeks.
I have not worked out the overall workflow yet but it looks like the basic software toolset is Picassa for general sorting and viewing with Lightzone for RAW processing and more detailed editing.
The completeness and ease of Photoshop Elements for processing NEF/RAW, managing images and outputting in a variety of fun formats is still pretty appealing. The counter-balance is that I use Linux as my primary desktop and would prefer not to deal with three operating systems (Windows for Photoshop Elements, Linux for almost everything else and Mac OS X for my iTunes which is on an old Macbook).