Here are some companies that are working together with OpenVZ project in one or another way. Feel free to add your company profile here.
Computer Tyme
Computer Tyme is using OpenVZ for their spam filtering service Junk Email Filter dot com. They are active proponents of OpenVZ; Marc Perkel worked at the OpenVZ booth during LinuxWorld Expo 2007.
Proxmox
Proxmox is using OpenVZ for their spam filtering appliance (see Proxmox Mail Gateway in VE). Proxmox is also the author of vzdump utility.