I book a booth each year at Toronto's Word on the Street festival. I sell copies of my books and handmade bookmarks.
These have really taken off because they are cheap and they wear out each year so people (who don't frame them anyway) need to replace them.
It's also great practise to loosen up my hand. I draw them in bits and pieces all year and then have about 100 of them ready for sale in September.
I'll post as I complete!