Grats on 40k! (I could make so many Warhammer references right now ...)
A couple of my programs i'm most satisfied with is exactly as you describe, non hardware related. I did a Database viewer and editor for a customer as they needed a frontend with selected functionality for the operators.
One other hobby program i've made is a Boardgame suggestion that mines some information from user profiles from Boardgamegeek and by setting preferrences suggests games. Basically a more advanced filter, but it turned out well.
/Y