The VM Workshop is an annual event (more or less) started in 1977 for systems programmers working with IBM's VM operating system. (None were held from 1999 through 2010.) It is informal and interactive with presentations on a wide range of VM topics by programmers from industry, education, IBM, and other software vendors. Most attendees come from North America, but there have generally been a few from Europe and elsewhere.
See the VM Workshop web site at www.vmworkshop.org for more information.