Tony Ruscoe found some internal Google subdomains. All of them have this form *.corp.google.com and include:
alien.corp.google.com
amd.corp.google.com
blackberry.corp.google.com
blueberry.corp.google.com
cluster.corp.google.com
cupid.corp.google.com
discovery.corp.google.com
gypsy.corp.google.com
ideas.corp.google.com
matrix.corp.google.com
paranoia.corp.google.com
While some of them have connections with existing or future Google services and Google employees, most of the subdomains have mysterious names.
Also see a list of public Google subdomains.
