I've also been using sneakemail for at least twelve years. They also let you set up addresses with a bunch of randomly generated letters/numbers that are opaquely mapped to you, but you have to log in to do that.
The only problem is that some sites ban their domains - in particular Adafruit does this (they banned existing use of it, not just new sign ups), and their support said basically "we won't whitelist your address even though you've been ordering stuff from us for over five years".
Re:Gmail trick: multiplying your address
by darkstar999 on Tuesday November 18, 2014 @11:28AM
(#8624622)
Also try 33mail.com for throwaways. You get a subdomain, so you can do [anything]@foo.33mail.com or [anything]@foo.33m.co
Of course it's also worth mentioning Mailinator.com (one-off throwaway aliases, but public) and 10minutemail.com (super-disposable temporary email addresses).