One easy way would be to use a disposable email address via DisposeMail.com as the alternative email address Google registartion asks. That way you don't have to register to any other site, and you could even use the disposable address to recover your account just by writing down the address somewhere - no expiration.
Of course, it's better if the disposable address is nothing somebody else might use, for example an SHA1 hash of something. Like
And if you want to be really, really anonymous you could use a bootable USB-stick for a separate, secure OS to protect from tracking methods like those used by Panopticlick, and of course route all traffic thorugh Tor... but I'm thinking you don't need quite that depth of anonymity. :)