The device will begin shipping to the early-access "Glass Explorers" within the next few days.
Google has made the interesting decision to not wait until enough products are in supply to meet the demand of its Explorer community, but to begin shipping in waves immediately.
A letter obtained by TechCrunch informs the 2000 "Glass Explorers" who signed up at Google's I/O Conference last year that the units will begin shipping in batches, with Explorers to receive a second email with all the details when their batch is ready.
This certainly suggests that Google isn't ready for mass production of general retail units, so for those who are not one of the chosen 2000 early-access users will need to wait for more announcements about general sales. At the moment, consumer units still aren't expected until 2014.