Use a "Contact us" form that they fill out on the website. This way the form mails the email, and the user will never know.
Or, for a less secure implementation, try this obfuscator:
http://www.aztekera.com/tools/obfuscate.php.
It converts letters to their HTML hexadecimal equivalents.
The advantages of this method is that everything functions as normal: Users can still click the mailto: link and/or copy and paste the email address.
Disadvantages: hasn't been thoroughly tested in the real world. Sloppy spambots will miss it, but I don't know how sophisticated spambots usually are.