We have seen these from backup products, specifically in our case Backup Exec 2010. They're remnants of the snapshot created as part of the backup and could be deleted safely.
A Consolidate-Helper snapshot is created by the VMkernel when snapshots are deleted on a powered on VM. Unless there's an issue with deleting the snapshots, the helper snapshot should be deleted again. If this is not the case, take a look at the log files to find out what's wrong.
