GNU Smalltalk (1.95.13a) is an implementation that closely follows the Smalltalk-80 language as described in the book Smalltalk-80: the Language and its Implementation by Adele Goldberg and David Robson.
To start: enter gst or gst -r or gst -q. The last two will suppress the performance statistics.
To exit: enter: <Ctrl>-d on an empty line.
GNU Smalltalk User Manual. This also contains a tutorial.
/usr/local/share/smalltalk/examples contains many examples. See the README file in that directory for information about the examples.
The book “Smalltalk-80 : the language and its implementation” by Adele Goldberg and David Robson.
If you don't have a browser handy while using Smalltalk and need some pointers or references try the command info "GNU Smalltalk". The info utility's interface can be a little daunting at first but is worth learning.