This may be totally useless but ... I accidently drag and dropped an Illustrator (.ai) file into an open Safari window and, after a long pause, it opened it with Schubert's PDF plugin. This also worked in Firefox.
This works for .eps files too. I guess it makes sense; PDF and AI are the same file types, they both begin with %PDF.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040612194402442