I've put a copy of UMASS Scheme in the directory:
ftp://www-edlab.cs.umass.edu/pub/cs287/
along with the lecture notes for the class "Programming Paradigms"
which I teach in Scheme (see http://www-edlab.cs.umass.edu/cs287/)
UMASS Scheme is an implementation with features that are used in the
class (opaque records, in particular). It also omits certain features
not required for the class. It comes with built in editor (for X-windows)
and rather minimal browser (for looking at the class notes within the
Scheme system).
UMASS Scheme built on top of Poplog, available from:
ftp://ftp.cs.bham.ac.uk/pub/dist/poplog/
It's also available from that site.
Robin.