Here are a few bugtrackers but I believe the free ones are all self-hosted.
You could also use Trello. It's not specifically for bugtracking but should work pretty well anyway.
Thanks again. I'll look into those trackers you linked me!
I am actually using Trello right now, but it's full of all my TODO lists and planned features and I don't want to make it public because it might disappoint people when I delay or remove planned features from an upcoming update, etc. It's full of lots of "nice to have" features and if possible I don't want to over-promise and under-deliver.
Maybe I should make a separate public board for bug tracking! I'm just worried about public boards being Trolled or vandalized. Might be worth a try, though.