Off the back of the Google Talk launch you can now get a free Gmail account (US only) via mobile phone. Even though there is still no sign up option on the Gmail site, most people who want an account have probably been able to find an invite, either from friends/relatives or from the Gmail Invite Spooler (sadly no more). Those without an account can fill their mobile number in on the Gmail site and recieve an invite via text message.

Everytime you get rid of your Gmail invites they seem to give you 50 more. It's clever really, it created a buzz and got people talking about the service and because you can't sign up directly you have to go round asking other folk for an invite. In reality there's plenty of invites for everyone.

Quoted from the Google Talk Press Release:

Google Talk requires a Gmail username and password, and starting today, Google is making it easier for anyone in the U.S. with access to a mobile phone to sign up for a Gmail account. When users visit http://gmail.com and enter their mobile phone number, they will receive an invitation code via a text message. This code enables them to open an account. With a Gmail account, users can try both Gmail and Google Talk, and begin inviting their friends and family to talk with them for free over email, IM or a voice call.