best non guitar rock solo

Keith Emerson's piano solo and synthesizer "steel pan" solo on Karn Evil 9 part TWO.
Rick Wakeman's organ solo about 2/3 into Close to the Edge

I second the Ian Anderson vote. The "rock flute" solo (that does give me a grin every time I say it!) on Locomotive Breath is quite excellent.

And yes, you really need to throw Geddy Lee in there. Cliff Burton's "Anesthesia - Pulling Teeth" also comes to mind.

The Fender Rhodes solo in The Doors' "Riders On The Storm"
Keith Eerson's solo in the live version of "Tarkus" from "Welcome Back My Friends To The Show That never Ends.."

Organ from In-A-Gadda-Da-Vida / Iron Butterfly
Swapped a lot of spit to this one...

Paul Butterfield's harmonica solo on "Everything's Gonna Be Alright"
Steve Winwood's Hammond B3 Organ on Hendrix's "Voodo Child"
Violin solo at the end of The Who's "Baba O'Riley"
Opening piano solo on Elton John's "Funeral For A Friend"
Bobby Keyes' sax solo on the Rolling Stones' "Can't You Hear Me Knockin'"
Ginger Baker's drum solo on Blind Faith's "Do What You Like"