Free Pascal is a free Pascal compiler for various systems including Linux, OS X and Windows. It is compatible with Turbo Pascal 7 and most versions of Delphi.
Free Pascal supports 32bit and 64bit architectures and can cross compile to systems using ARM, such as handheld systems. As long as non system dependant libraries are used a program written in one environment should be able to be compiled and run on another, for example Windows to Linux or vice-versa.
Free Pascal has an IDE called Lazaurus which makes coding in Free Pascal a breeze. Currently Free Pascal can create GUI applications for Windows, OS X and on Linux it can use GTK 1 and 2 and QT support is nearing completion.
