How do I backup and restore SMS Messages?
I highly recommend SMS backup+. It'll back up your SMS to a Gmail Label:
Automatically backup SMS, MMS and call log entries using a separate label in Gmail / Google Calendar. It is also possible to restore SMS and call log entries back to the phone (MMS not supported yet).
You can use SMS Backup & Restore to export to an XML file:
Schedule automatic backups or backup your messages anytime you wish. You can view backup contents on your phone, and choose to backup selected conversations only.
Backups are created in XML format and saved to your device's SD card.
The XML can then be converted to other formats, and can also be viewed on a computer.
It's easy to e-mail your backup files anywhere you wish.