How can I signal that I don't intend to follow up the items in my "Future Work" section? I'm currently writing a paper that is based on work that I won't be following up on, as I'm changing career directions. I believe that the work raises a number of questions and ideas for future work, and my program solves a number of the boring problems without getting into the interesting applications. However, I've previously been told that raising an idea in a "Future Work" section effectively 'reserves' that work for me, and it would be considered rude for readers to begin research on those areas. 

How can I signal (without flat out saying that I don't care) that I hope others will pick up and run with the ideas I'm presenting?

If it's of any importance, it's a Computer Science paper.
I've never heard this about "Future Work".  Items that you put in this section are simply things that you are currently considering, and someone else who does them should at least cite your original work.  However, anyone who beats you to actually doing the work should be able to publish it.

If you want to make it absolutely clear that you do not intend to work on this material (and, you never know, you might end up going back to it later anyway!), simply call the section "Further discussion" or just "Discussion".