LinkedIn and GetGlue both require logins to unsubscribe, so I mark their emails as spam and filter directly to trash. It works, but philosophically it still pisses me off...
You can give a custom email to every website. Then if they spam you or sell you address, you'll know and it's one click to turn them off.
Another nice trick is to change your email at a spammy vendor to a leemail and then turn it off.