The NATATA Anti-Spam Encoder is a simple utility for turning mailto: links on HTML pages from addresses harvestable via spambot to mailto links human-readable via web browser, but not to simple spambot screenscrapers.
It's very easy to use, and there's no downside to using it on every single page within a website. Only the spambots will know the difference.
Downloading and installing the HTML Reference Library is a good idea for Windows web developers.
Simple mailto: encoding is not appropriate for commercial sites or personal sites in which the privacy of the owner is important. A cgi formmail script should be used when the destination of the mail is never publicly visible.