Fellow vExpert Rod Gabriel, the Wisconsin Area VMUG Leader points out that a VMUG registration is required in order to be invited to the VMWorld VMUG activities and get the official VMUG shirt.
For those of you who are attending VMworld, you should make sure to be officially registered as a VMUG member. There should be some VMUG member shirts available for you there as well as some specific VMUG activities. You will need to be registered as a VMUG member in order to get the shirt and to be invited to the activities.
Here is the link to officially register as a VMUG member: http://communities.vmware.com/community/vmug/localgroups
There will also be a VMUG booth there separate from the VMware booth so be sure to stop by and check it out.