Seth contributed to Firefox Hacks!
Seth Dillingham: My Contributions to O'Reilly's Firefox Hacks
Seth is now a published author, having contributed 5 hacks to the new Firefox Hacks book from O'Reilly. Since Nigel wrote the majority of the book, Seth isn't listed as an author on amazon.com or on the cover, unfortunately, but of course his name and those of other contributors are listed in the book (see page 'x' in the prefix).
By the way, Seth has written quite a bit about Mozilla and Firefox, so check out his site for even more useful information.