[misthop]

gmail actually is set up to handle this. You can append +<text> to an address to create a targeted one-off (so if your address is [e-mail], you could do [e-mail]) Of course you then have to set up a filter on the gmail side to label it/send it to spam if intrusive.

The problem with this solution is that many email harvesting widgets incorrectly see +xyz as invalid, even though it satisfies the rfc just fine.