This trick is free and easy. Just copy and paste these comments into each page's header. (Or make up some anti spam garbage of your own.)
<!-- WPOISON WPOISON WPOISON WPOISON WPOISON WPOISON WPOISON WPOISON WPOISON -->
<!-- mailto:@@@@@@@ MailTo:@.@.@.@ @.@ .@. .@.com .@..com
error@invalid@page@exception@hahahaa!!!mailto:: @nospam mailto:@NOSPAM.com firstname.lastname@example.org
spammer at dot dot com fakeaddress at dot com dot com dot com dot
com dot com $?®¶??å?¾ø@hotmail.com &&$@blah.n?t
We like it when email harvesters crash
How it works:
1. Many spambots are programmed to ignore files with anti-spam software. Wpoison is a well known one.
2. The other garbage is sure to give a spambot indigestion. It might cause it to crash, or give an error message where the user has to click "OK" before the program continues to run. Often these mail harvesters are left running all day and night, so they would lose many hours "work".
1. The spambots could be programmed to ignore things in comment tags. But that would require extra processing power. The harvester would run much faster just searching for strings that look like email addresses, so either the spammers are slowed, or won't bother looking for comments.
This idea not invented by me, so don't give me the credit for it. It originally came from a "Counter-Exploitation" web site that disappeared somewhere.
Hope that helps!