GDocBackup Makes an Offline Backup of Google Docs [Downloads]
After installing the utility, simply enter your Google account details into the configuration screen, pick a backup folder location, and click the Exec button to download all of your documents. You can even choose the format that you want to export them as—so if you wanted to download all presentations as PDF format, you can easily do so. Once you've run a backup once, the utility will only backup changed files on subsequent backup jobs—even though the backups are manual, it's still worth a look if you want a simple, non-instrusive method for backing up your Google Documents.
GDocBackup is free and open source, available for Windows only. Readers using Linux or Mac can check out the GDataCopier Python script, or OpenOffice users can use an extension to sync documents back and forth.