Use FolderSync. I was using it to sync folders with Google Docs. After upgrading to Google Drive, sync still works. I have just tested by adding new Google Drive account. Google Drive is fully supported. Just, choose
Google Docs when adding account in the app.
In case, you don't want to pay, its free lite version is also in Play Store, but with some limitations.
It supports two-way sync as well as one-way sync (up or down). You can use its up sync for backup purpose. It also supports filters based on size, extension etc. So, if you want to backup all photos from your SD card, the app is good to go. It features
Delete after Upload, too.
You can schedule sync jobs, too. So, it can do backups automatically without any hassle. The best: It features
Instant Sync. If you turn it on, files will be synced as long as they will be modified or added in folder.