Not many of us are blessed with huge blocks of time, either. Again, it can be very satisfying to do just a little each day, or a few times a week, and watch the stash of items grow, slowly but steadily.
It's difficult to choose between a huge national cause and your own local area's needs. Maybe you can choose one of each. Or, stick to just one. The main thing is that you care enough to do a little. If each one of us who enjoys making things with our hands, whether for sale or for gifts, if we only did a few things a month, that would be exciting - it would be marvelous - it would help more than any of us could even imagine.
Searching the internet for causes can jumpstart your ideas, get you excited, and motivate you. Even if you do not choose one of those you find, and you decide on something local, you can get ideas from all the folks who are already doing this. Start with just the words "charity crafting." I just did that and I ended up with 8,640,000 hits! You could narrow it down by adding a word to describe your craft as a third word in your search (knit, crochet, sewing, whatever).
Go have some fun. Feel good about yourself. And make someone else feel good, too.