A poster at the Aaron Sorkin Yahoo Group (registration required) claims that Bradley Whitford has signed on for "Studio 60 on the Sunset Strip", saying that Whitford was scheduled to direct episode 21 of the "The West Wing", but will not be able to due to the fact that "Studio 60" starts shooting on the 14th of March. He also mentions that "Studio 60"'s soundstage will eventually be on the "West Wing" soundstage. In the past, this poster has talked about shooting the "West Wing" episode with Jon Bon Jovi and posted an anecdote about John Spencer and Martin Sheen.
Another poster at that group has posted a very interesting early draft of the "West Wing" pilot in the group's files section.
Amanda Peet Interview and Full "Studio 60" Script
First Casting Announcements
Previous Casting Updates
Various "Studio 7" Updates
Matthew Perry Rumor
Round-Up of Info
Info on accessing the audition script.
Praise for the show
"Studio 60 on the Sunset Strip" Discussion at "Television Without Pity"