He was already on the ballot when he resigned, and did not remove himself from it (or perhaps could not due to deadlines? I'm not sure). It's an interesting situation, to be sure, and none of the write-in candidates have run particularly loud campaigns (or I haven't heard a word from a single one of them, anyway).

I found this article via Google that covers some of the issues and people. (http://insidemedford.com/2008/09/10/register-of-probate-buonomo-resigns-is-still-on-ballot/)