I was checking out Zophar's NES development tools section, and saw a NesDevKit that was placed on that site in 2002. I went to the site that it was from (the below sourceforge link), and noticed that this was updated in October of this year. I grabbed it, but it looks like it's still young. I haven't messed with it any yet really, I just thought I'd let everyone know who might not... I don't recognize the people's names, but maybe you might know them: Robert Guite, and Mekanizer. Anyway, here's the link.
http://sourceforge.net/projects/nesdevkit/
http://sourceforge.net/projects/nesdevkit/