I just made the mistake of putting my extra Gmail account invites on e-bay. It looks like the going price for a G-mail account is .05¢. Surprisingly, most people are offering FREE SHIPPING!!! Go figure, an electronic invitation comes with free shipping. Who'd have thunk it?
If you're not looking to makea buck, but be nice and share the wealth, you can give them away here, at Gmail Swap. There's also a Gmail spooler service here at isnoop.
If you already have a Gmail account, you can get the Gmail notifier here. It will tell you when a new gmail has hit your account, just like outlook.
1 hour ago