The Other Donna sent me a link to a yarn manufacturer's webpage for finding various crafting charities. The first one that caught my eye is called Chuck's Hats for Chemo. It's a charity that makes hats for chemotherapy patients.
I'm right in the middle of a different project right now, but I can easily see myself getting involved with that project. I've already made a hat, so I can vouch for the fact that the process is pretty straightforward. It also doesn't require tons of yarn,l so I'm thinking that I will now have a good use for the yarn that's left over from skeins after I've completed projects. And, of course, there's always the possibility of just picking up some yarn that's specifically FOR making a batch of hats, rather than simply waiting until I've made something else and have leftover yarn to use.
If my goal is to always have a project going at any given time, this is just the sort of thing that I can stay occupied with for the long haul, even at the times when I don't need to make any new items for myself or family/friends.