MS: 
Revenue  US $51.12 billion (2007)
Employees 79,000 (2007)

IBM:
Revenue  $91.4 billion USD (+4% FY '05 to '06)
Employees 355,766 (2006)

Rotten Apple:
Revenue US$24.01 billion  (TTM FY 2007)
Employees 17,787 full-time; 2,399 temporary (September 30, 2006

Novell:
Revenue US$1.2 billion (2005
Employees 5,006 (2006)

Red Hat:
Revenue $278.3 million USD (2006)
Employees ~2200 (April, 2007)

Oracle
Revenue $17.996 billion USD (2007)
Employees 68,236 (2007)

SUN:
Revenue US$13.873 billion (FY07)
Employees 34,600 (2007

Canonical:
Revenue $10m+
Employees 130