mailinator- i still use it sometimes

you can assign yourself an email address, whatever you want it to be. i usually choose susanq@mailinator.com. use the address on some site where you want to validate you have an email address without actually giving them your address. then go check your email on mailinator:

http://mailinator.com/

and grab the validation link, or whatever information they've emailed you. then you're done with it. they don't have your real address, you have their 'service', mailinator dumps whatever junk mail you get from them on a regular basis.

good, clean, fun.