A couple of others to add to your list:

• O'Reilly employ Nat Torkington, Jon Orwant and Larry Wall
• SlashDot employs Chris Nandor (MacPerl pumpking)

And a few updates to your list:

• Brian Ingerson hasn't worked for ActiveState since last summer
• I think japhy left RiskMetrics to go back to school
• The Canon Research Centre is in Guildford, not London

Update: Oh, and also the list of Stonehenge instructors rather implies it's not a one-man shop :)

"The first rule of Perl club is you don't talk about Perl club."