George Gassaway has built numerous R/C shuttles that launch as a rocket, drop SRBs and External Tank, then fly back under R/C control. You can find information here http://members.aol.com/GCGassaway/rcgliders.htm

I haven't seen or heard of any that were dropped from an airplane. That's not quite a standard Space Shuttle flight profile.

However an X-1 or similar rocket plane dropped from a B-29 is nicely scale and has been done. George's X-1 boosted as a rocket, not dropped. But here's a video of an X-1 being drop launched http://www.flixxy.com/rc-plane-b29.htm