Smalltalk is a pretty distinct OOP language that is really good to demonstrate the power of the object orientation itself. Also, this language can be used as an example of the truly integrated desktop environments: Smalltalk IDE is embedded into the language's VM and written in Smalltalk - and pretty hackable too! One can just open the REPL-like dialog window and send messages to the "Close" button of some randomly selected window and see instant feedback!
- Pharo, the modern Smalltalk environment originally derivated from Squeak/Smalltalk
- Glamorous Toolkit, "the moldable development environment. It is a live notebook. It is a flexible search interface. It is a fancy code editor. It is a software analysis platform. It is a data visualization engine. All in one."
- Squeak/Smalltalk, an integrated ST environment with Morphic /GUI very suitable for education. Can run under the /Raspberry Pi
- GNU Smalltalk
- Original Scratch
- "Experiencing Smalltalk", an interesting article with the author's impressions about using ST.