There's an odd little application that's been brought up that's written in PHP with one purpose - obfuscating an email address/HTML so it's very difficult for a spambot (or other harvesting program) to get a hold of the content and add to its list. The Obfuscator takes in an email address and, with the click a button, spits back out the obfusicated code.
They're also offering the source for the application so you can get behind the scenes and see how it works. It definitely does a good job at making things more difficult, but I'm not sure how useful it really is in practice. If you're just using it to drop into a one-time kind of location, it would work, but the results this thing spits out would be a nightmare to maintain (especially the HTML).
One good thing, though, is that too the user, it all looks seamless. There's no funny characters or things they'd have to change in their browser to get it to work.