One of the most common ways that spammers get e-mail addresses is through webpage harvesting. They crawl thousands of pages looking for e-mail addresses; if they find one in the form of myuser@mydomain.com they'll add you to their databases. For more info read this interesting study.

enmDespamify will help you "hide" your addresses by translating them into HTML character entities (for example 'a'=a 'b'=b etc).

Just type in your e-mail address, click encode, and the replace every occurence of your address in your webpages with the encoded version. Your browser will render it as a normal looking e-mail address but it is MUCH harder for them to extract while crawling your site.

If you're interested in seeing the source code for this program, click here

Good luck...