Google has a cool little surprise in store for heavy e-mail users (and Mac owners): Google E-mail Uploader for Mac. It's a free app that can archive your old e-mails from Apple Mail, Eudora and Thunderbird on your Google Apps e-mail account.
It's actually a great idea; chances are that in the pre-cloud era, you've had tons of e-mail stored somewhere in your desktop e-mail client. Now, you can move everything to the cloud in one easy step.
If you're a Windows user, check out the previously available Google E-mail Uploader for Windows. Unfortunately, you can only upload your e-mails to Google Apps e-mail accounts, not your gmail.com or googlemail.com accounts.