Having tried a bunch of different methods in the past, my answer, at least as far as "unspammable" goes, would be "You can't."
Even with your image technique, or no matter what else you do, as soon as somebody does e-mail you they'll have your address in their address book. And then they'll get infected by a virus that steals their address book and sends it to a spammer.
Frankly, if it's your own address, I wouldn't even bother. Just set up a separate e-mail account for your web-related e-mails and use a good adaptive spam filter on it. Remember to occasionally skim your spam folder for false positives.
If you're dealing with addresses belonging to other people (e.g. your users), it does seem prudent to exercise a little extra care. In fact, the first question I'd ask myself is whether you even need to reveal your users' e-mail addresses in the first place. You can always implement an "e-mail another user" feature on your site without actually revealing the recipient address to the sender. At the very least, I'd say that making their e-mail address public should always be optional (and opt-in, not opt-out) for the user.
I would also suggest that you probably shouldn't show a user's e-mail address to anyone who isn't also a registered user of your site. This may not stop all address harvesters, but it should stop the majority of them. Preferably, you should also use a good CAPTCHA as part of your account registration process, and you may also want to wait until a new user has participated enough on your site to confirm that they're not a bot before granting them access to abusable features such as other users' addresses.