For reseller accounts:
1) Backup to another server nightly in the same DC.
2) Weekly we copy those backups to a NAS unit in the office.
3) At the reseller's request, free annually we'll mail a cd/dvd with the weekly backup on it - after that it's $5 plus shipping
For VPS'es:
1) Daily rsync to a remote server in another DC with 7 days of archives
2) Nightly vzdumps to the same server
3) Weekly backup of the vzdumps to the NAS in the office
4) Annually cd/dvd free, $5 + shipping for additional
While not backup... All of our server have at least RAID 1 if not RAID10 arrays. We had a drive go out in a VPS node about a week ago. A replacement was overnighted direct to the DC, hot-swapped and re-sync'ed. During that we started copying the vzdumps (much easier to restore from) offsite just in case of another failure - we could move them to another node quickly if need be. If it wasn't for our sending out announcements about the drive failure, plan of attack, and status updates - I don't think the customers would have even known...
But I'm a FIRM believer in multiple backups in multiple locations... and we don't count backups towards bandwidth or disk quotas. That's just something we figured into offering a 'wholesale' product that others are counting on. We do also strongly suggest customers make their own backups - if it were my business I would.