One of the frequent questions we've heard during our IT Camp Events is in regards to virtualizing USB devices for use within child VMs on a Hyper-V host. While there's no native out-of-box support for this, I did want to call out a third-party solution that I've used with several customers and works great: Digi's Anywhere USB.
As a network-attached USB hub, Digi's product provides USB device access over TCP/IP … much like we did with Serial over IP in the old days of dumb terminals, but this time with USB devices instead. Digi provides driver support for Windows Server 2008 and 2008 R2, as well as down-level support for Windows Server 2003.
NOTE: This solution doesn't support USB storage devices or USB modems, but that's generally not needed when we're talking about Hyper-V because there's usually much better ways to virtualize those devices than using USB devices 🙂
These devices are not enormously expensive and provide a great supportable solution when USB device access is needed from within Virtual Machines.