Many more vendor-specific training options are available now than even a year ago, but vendor-neutral opportunities remain meager. Although “virtualization” is a general topic conceptually (like security), virtualization is still very much tied to particular operating systems and environments.
For training on a specific platform, visit the vendor’s website first. Then look at other training companies such as Train Signal and Global Knowledge to compare offerings. Regardless of which source offers such training, expect to pay $1,000 or more per day in the classroom (or for per-day equivalents online).