We modiified bento to support vsphere : https://github.com/ii/bento/tree/vsphere
You need to set some variables to export to vsphere:
#Path is to a local build from source of commit 37fe7647279ed79ec86020b7852e08f04b079dcc
export PATH=/tmp/chrisgo/src/github.com/mitchellh/packer/bin/packer:$PATH
export VI_USERNAME=DOMAIN\\XXXXX.cmcclimans
export VI_PASSWORD=XXXXXX
export VI_HOST=vsphere.MY.com