Unusual Shaped Bee/Wasp Nest
The photo is fuzzy, so we cannot see whether the nest is papery or of mud.
If it is papery, it is a bald-faced hornet nest.http://extension.umd.edu/hgic/bald-faced-hornets
If made of mud, it is a mud dauber nest.http://extension.umd.edu/hgic/insects/predatory-wasps
Both of these are beneficial insects (they feed on pest insects) and should not disturbed if possible. We need them to keep down mosquitoes, etc.