This Digital Alchemy article describes how you can use a plus sign (+) to add a sub-email address to any gmail address....

" Gmail has an interesting quirk where you can add a plus sign (+) after your Gmail address, and it'll still get to your inbox. It's called plus-addressing, and it essentially gives you an unlimited number of e-mail addresses to play with."

" Example: If your address is pinkyrocks@gmail.com, you could use
pinkyrocks+nytimes@gmail.com for nytimes.com
pinkyrocks+freestuff@gmail.com for freestuff.com
Then you can tell which site has given your e-mail address to spammers, and automatically send them to the trash. "

Eeeeenteresting....