Gmail is Google's somewhat-new free email service. It's much like hotmail, yahoo mail, or any of the others, but I (and many others) believe it's better. They give you 1GB of storage, which is more than most or all of the others, and the interface is very nice and well thought out. It is invitation only, because it's still in 'beta', but seems to be pretty near completion.
I'll just need your email address for anyone who wants to sign up.
You can read more here -
Gmail Info