Here are some great resources:
- a nice, gentle tutorial — Learn Smalltalk with Prof Stef
- the most actively developed Smalltalk — Welcome to Pharo!
- a free book — Updated Pharo by Example
- a MOOC (massive open online course) — Live Object Programming in Pharo
- some great videos — Smalltalk 4 You
- a book that I like (not based on Pharo) — Smalltalk by Example
- another book that I like (not based on Pharo) — Computer Programming using GNU Smalltalk
- some additional resources — Resources
This book (not free) is my favourite for learning how to use Smalltalk for object-oriented programming: Smalltalk, Objects, and Design, by Chamond Liu.
I myself have published a whole bunch of Smalltalk tutorials. The latest ones are:
IMPORTANT UPDATE: There is a new Pharo MOOC that starts on October 16th, 2017. Sign up now!