Nick Jamil and Jeff Balogh have posted a fairly detailed design for DrProject's new ticketing system. As far as I know, there isn't another one like it: when a project is first created, its ticketing is just a to-do list, but users can add extra fields (like "owner", "due date", or what have you) to meet their needs. I think the initial low cost will make ticketing more attractive to undergrad students; I'll be very interested to see what information teams (undergrad, professional, open source, or whoever) choose to add when they're given complete freedom.