One way to cut down on spam is to decrease exposure of your e-mail address (of course, this doesn't help with dictionary attacks
Most of us know about usenet and whois as huge opportunities for spambots. Another is having your e-mail address on a web page.
Turns out, there are relatively few IPs from which spambots surf. Blocking access to such IPs will at least help decrease the number of e-mail addresses they have (and cut down your bandwidth usage).
I've also noticed that spammers are starting to use caches from Google and Yahoo. Keeping Google from caching your pages (or at least using php to hide your e-mail address when spiders hit your pages) can help. (If you're feeling a bit more agressive, substitute "email@example.com" for your e-mail address