Gmail address features: + and .

Wow. So if your email address is fredflintstone@bedrock.info you can start using fred.flintstone@bedrock.info any time you want. Gmail will treat the two identically:

Official Gmail Blog: 2 hidden ways to get more from your Gmail address:

...Append a plus (' ') sign and any combination of words or numbers after your email address. For example, if your name was hikingfan@gmail.com, you could send mail to hikingfan friends@gmail.com or hikingfan mailinglists@gmail.com.

Insert one or several dots ('.') anywhere in your email address. Gmail doesn't recognize periods as characters in addresses -- we just ignore them. For example, you could tell people your address was hikingfan@gmail.com, hiking.fan@gmail.com or hi.kin.g.fan@gmail.com. (We understand that there has been some confusion about this in the past, but to settle it once and for all, you can indeed receive mail at all the variations with dots.)...

The trick with the + suffix is very old, I think it might be a unix thing. It's neat to see it work in Gmail.

Personally, I prefer to use disposable Bloglines email addresses for the sorts of things the + suffixes are used for.