>>1
freepascal.org
I haven't used any of these, but I have this note:
Borland Turbo Pascal 5.5 is available for free and still used in some University intro courses. That was the last version to use the textual IDE.
Delphi replaced Turbo with GUI and fast prototyping. Delphi's language is object oriented Pascal. Lazarus is a free clone.
Free clones of Turbo are Free Pascal (freepascal.org) and Virtual Pascal (not open source).
1/2007.
Niklaus Wirth designed Pascal and published a compiler for Pascal and another for PL/0. Wirth later moved on to Modula-2, Modula-3, and Oberon.
Interpreters
GHLI is embeddable script for PAscal snd assembler.
http://sourceforge.net/projects/libghli/
General Purpose Interpreter
http://sourceforge.net/projects/gpint/