GMail is semi-public right now, and is about to come out of Beta testing anytime this year. Also every GMail user is got 50 invitations to his account which he is free to distribute. However, this is not the way to spread GMail to the public.
If you have no such friend who would invirte you , Hello. Im Keerthivasan Rajamani, and im your new friend. :)
Mail me - keerthivasan at gmail dot com
Otherwise you could yourself go to http://isnoop.net/gmail/ and get your own GMail invite and further get your GMail ID. Go Fast !