What and Why is Squeak?

What is Squeak?

Several answers:

Squeak is a free, portable, robust, full-featured implementation of Smalltalk-80. It runs on a variety of platforms from "bare chips" and pocket WindowsCE computers to Macintosh, Win95/NT, and most flavors of UNIX. Squeak is distributed with all its source code.
Squeak is the rebirth of the original Xerox Smalltalk-80 with the goal of "burning the disk packs" and moving down a new research path, away from the one that commercial Smalltalk took.
An amazing multimedia development and delivery tool featuring sound recording, playback and generation; multi-threading; color at any depth and resolution; animation capabilities; great Web serving and help-application capabilities; and the best development environment around.

Why Squeak?

Let me give you my answers, why I'm personally using Squeak:

As a pedagogical tool: Using Squeak, my students can explore a large range of exciting applications (from graphics to sound to non-WIMP user interfaces to Web-based tools), and have the source to absolutely everything to explore.
As a research tool: Squeak has two roles for me in my research. First, since it's highly malleable, I can tweak it (e.g., provide a new collaboration tool or a new visualization tool) and study how my students use these tweaked versions. Second, it's so much better than any other tool that I've been using: Faster, more-portable, and better development environment.

Where do I get Squeak?

http://www.create.ucsb.edu/squeak