Sure, everyone knows about creating spam-trap addresses at places like Yahoo. Here are a couple of different ideas for fending off spam that you might find a little more elegant, for two different email-requiring situations.
For mailboxes you know you're only going to need once or twice (and for which you have no concern about the security of those emails) check out Mailinator.com. An example here might be a sign-up with a newspaper where all you need is one email from which to pull your new password, and after that you'd like the box to go away.
The Mailinator server(s) will, on-the-fly, create a mailbox for anything addressed to them, and in a few hours delete it. This is perfect when The Omaha Daily Bugle demands registration for some article you want to read, and after that transaction you need nothing more from them. You register with your bogus personal information, just as you do now, but you make up a box name at Mailinator and plug that into the Bugle's form (remember, you don't have to actually create it at Mailinator). The newspaper sends your password to whatever impromptu box at mailinator you entered into the registration form; you go there and enter that mailbox name and get your password. Not long afterward, the box just goes away. Mailinator itself requires no registration and the field for entering the temporary box name is on the home page. Quick'n'slick. Check it out. Free; accepts donations.
Note, though, that this is a niche service, to be used when you do need an email or two, but only those. Using it as a general spam trap address, such as flying it in your Usenet postings in your From header, is abusing that server and service, because that's not a case where you need a working, temporary box on a very short-term basis.
Another approach is that of Sneakemail.com. and it's an excellent way to handle registrations for places with which you do wish to maintain a line of communication, but lets you see they've sold your address to spammers or shared them with odorous partners - and to whom - and close that door immediately. You could use this method with your hometown newspaper when you register to read the local buzz on that fire at the bagel works, but want to also get on their mailing list for something or other.
You create a proxy address at the Sneakemail site, having it forward to the real email box where you'd like to receive mail from. You provide that proxy address to The Dubuque Tribune. When they send their mail to you via that Sneakemail address, it's forwarded to you at whatever real mailbox you've specified. Fine. Life as usual. But the kicker is that this works both ways you can reply to that forward and the receiver sees it as coming from the Sneakemail address you created for them and still doesn't have your real address. And since you've only given that address (the proxy address) to the Tribune, if you get something from anyone that comes through that Sneakemail address you know your address been sold and you can just delete the proxy. You can use one such address per correspondent/company/whatever, or you can give it to more than one (remember, it's just an address) – but that reduces the precision with which you can cut off spam (when you delete the proxy, you've killed communication with everyone that you've given it to). I think this is as slick a solution as Mailinator, but for a different situation. Free; has a premium level with more features.