We use Percona's XtraDB streaming backup to take backups of our smaller databases, and incremental backups of the larger DBs. We store them in a series of places: on a backup instance within east-1, on a second dedicated backup instance in west-1 (in case east-1 ever bites the dust completely, such as during hurricane Sandy), and then long-term archival on S3. S3 is good for smaller databases but for our biggest ones it takes multiple hours to download a full archive, hence the backups in multiple places.

However, our primary strategy for uptime is redundancy -- every db has at least one slave, and we are spread across multiple availability zones.

Any good resources for XtraDB's streaming backups? I'm looking to move in that direction early next year.

We are planning a follow-up blog post that goes into more technical detail about our backup and restore strategies; look for it in a week or two.

did you ever examine DRDB (I think it is integrated into some of the Linux kernels)?

With postgresql, you can do streaming replication to a few machines. I have one large machine on standby, and then a couple really small ones, some on a different provider that just receive the updated db data using pg_receivexlog.

Stuff not in a database goes on S3.