ASCEND is an interactive environment for modeling, debugging, and solving large systems of nonlinear algebraic or differential equations. Oriented towards chemical engineering applications, it includes a large Open Source thermodynamic properties database. The interactive design allows users to inspect and solve very difficult nonlinear systems. It includes plotting abilities and is scriptable using both Python and Tcl/Tk.
ActiveTcl is a Tcl distribution available for many operating systems. It is complete and easy to use, and offers quality-assured ActiveTcl Business Solutions. It also offers ActiveTcl Enterprise, which gives you support and maintenance packages for your company. The ActiveTcl OEM licensing provides you full redistribution rights, plus optional support and co-marketing packages.
Alana is a highly responsive Turing Machine simulator with many examples, like (unary and binary) addition, subtraction and multiplication, "copy band content", string parsing examples, and divisibility and primality testing. The documentation contains an introduction to Turing Machines as well as some interesting theoretical information (halting problem, busy beaver, universal Turing Machines) and pointers to further literature.