if I may sink into blind conjecture for a moment, it could simply be that the project doesn't yet exist so hasn't "sparked your interest" - I know I don't personally take on projects that don't interest me (and yes, being paid makes it interesting) because I'm likely to get bored of them. That's why that, although this thread is fine for ideas, you'd really need to find something that "clicks" for you, a problem that interests you beyond simply serving as a curiosity.
A good example from my personal experience is this: if I try to take on, say, a downloads manager add-on for XenForo, I'd lose interest very fast as it doesn't have any interest for me or for my forum's users. A gallery, however, definitely would as my community is very creatively inclined, and some fancy IRC integration would interest me because I like XenForo and I like IRC and there's very little available on that front. Find something that makes you think "yes, I really want to see this problem solved," do it, and make sure you're doing it for the satisfaction of the job.
Unless you'll charge for it, in which case replace "satisfaction" with "cold, hard currency."