Large and small companies that use weblogs
Companies that do weblogs:
Lotus: Ed Brill
Macromedia: John Dowdell, Mike Chambers, Matt Brown, Vernon Viehe, and Bob Tartar .
Groove: Ray Ozzie.
Microsoft: Joshua, Andrew Conrad, Benjamin Voigt, Chris Anderson, Chris Hollander, Dare Obasanjo, David Weller, Don Box, Douglas Purdy, Harry Pierson, Jimmy Grewal, Joe Beda, Joe Bork, John Lambert, Keith Ballinger, Matt Williams, Michael Winser, Peter Drayton, Rob Fahrni, Sascha Corti, Tantek Çelik, Tim Ewald, Wolfgang Manousek, Ziv Caspi
Radio Userland: Dave Winer
Moveabletype: Mena G. Trott
Jupiter Research: David Card, Michael Gartenberg, Joseph Laszlo, Robert Leathern, Lydia Loizides, David Schatsky, Gary Stein, Robert Sterling.
I'm sure I have only scratched the surface - please add in the comments and I'll add them here.