Hi,
Here's how I'm doing it on my site. When a viewer clicks on a "Contact Me" link, he/she will be taken to a page with a dynamically generated GIF of some random text that he/she will have to type into a textfield. Only when the proper text has been entered, will he/she will then be redirected to a mailto URL which would automatically open his/her email client. The GIF is generated using GD. The email only appears inside the code, none in the form or html pages. Now, in my case, I only have one email address so I was just able to hard code it. You will have to modify or combine with the other schemes discussed in this thread so far to make it work with multiple addresses.
The purpose for doing all this is so I can't be spam, and I am fairly sure that it is a person sending me an email rather than some program.
Hope this helps.