Can I recommend an amazing improvising cellist? Zoë Keating has invented a fantastic technique of real-time layering of sounds from her cello, using a pickup connected to a sampler and loop-back system. The setup is controlled by foot pedals as both hands are fully occupied obviously!
Here's her web site http://www.zoekeating.com and on the "Projects" page there's a set of free MP3 downloads of short exceprts (Exurgency/Walking Man/Arrival/Updraught/Coda ).
She rocks!
Hope this is OK to post.