simple to use, good in service Rated 4 out of 5 stars
Maskme is a simple-to-use add-on which makes it possible for you to use sites which normally would require your personal information, without actually giving them it.
I use it mostly for mail. If you're not sure if a site has really something to mail you, or is just trying to get your mail to spam you; just use maskme, fill in another, completely random mailadress (literally takes one click) and STILL get the mail from the site forwarded! if the site only sends spam, just delete this mail and don't be bothered.
If you're mostly concerned with your privacy, then this add-on is certainly a good idea, too, since it blocks sites from knowing your information. Also, check out DoNotTrackMe, also from abine, it's great for blocking (obviously) trackers.