Nels Cline
Nels Cline has done a ton of work (both recorded and live) with Thurston over the years. They once even recorded a studio duet, and officially released live duet together on the same day! Nels Cline has released a mariad of discs over the years, usually under the name The Nels Cline Trio, and recruiting the other two performers accordingly. He also has a new trio record coming out this year under the name The Nels Cline Singers, which is still instrumental. Plenty of info can be found on Nels Cline on his official site nelscline.com.
Toshi Makihara
Philadelphian percussionist Toshi Makihara plays a large part in the improvised music scene. As well as working with Thurston, he has done improvisations with John Zorn, Nels Cline and William Parker to name a few. His style has been said to be influenced by vaudeville humor, and the jazz school of thought that says that silence can be used just as effectively as any of the notes you could play (or fills, rolls, etc when thinking of drums). Toshi's set is usually made up of only a very minimal drum set, and often lots of random objects he finds that he feels may do the job. Lot's more info on Toshi can be found here.
Zeena Parkins
Zeena, like many of the performers that have worked with Thurston is a very ambitious and prolific musician. Mainly working as of late in the form of chamber music. She has also worked with many other composers, the infamous John Zorn being one of them. There is a great deal of info about Zeena's life and her music on this website here.
Wally Shoup
Wally Shoup has been a mainstay of improv music since the late 70's. He played an instrumental part in starting the Seattle Improvisational Music Festival, as well as the Other Music Series, which visually inspired Sonic Youth's own SYR series. Shoup has been well known for his equal love of musical improv and visual art.