Linode's backup system includes a snapshot which can be triggered whenever you like, as well as the scheduled incremental backups.
The UI looks like this: http://img16.imageshack.us/img16/3251/linodebackups.png
The UI looks like this: http://img16.imageshack.us/img16/3251/linodebackups.png
from: http://www.linode.com/backups/
Files that have been modified, but are the same length and without any metadata changes (like mtime) will not be considered "changed" during a subsequent incremental backup. Currently, only ext2/3 volumes can be backed up (this limitation may be removed in an upcoming release). ACLs and extended attributes are NOT tracked.
The slice version is: http://www.slicehost.com/questions/#backups