There are lots of hits on a "special typed characters" search. Here are just a couple to check out. http://home.earthlink.net/~awinkelrie/keyboard_shortcuts.html
http://www.origins.tv/htmlataglance/characters.htm
Occasionally I might use the ALT+xxxx command, with the xxxx being four digits. i.e. ALT+0185 is the ¹ you asked about. There are nearly a Zillion other characters available for who knows what.