Encrypt your GMail with Firefox and GMailEncrypt
While this won’t help with e-mail indexing on the Google servers, it will provide a small modicum of privacy on your GMail communications. UneasySILENCE points out the Greasemonkey script called GMailEncrypt and the relatively simple steps for the encryption and security key generation. You’ll need Firefox for this approach that encrypts at the local level; if any commenters know of other simple approaches, be sure to share!
