C-Intercal Compiler - William Patterson's DOS port of the classic Intercal-to-C compiler coauthored by Eric S. Raymond.
C-Intercal Supplemental Reference Manual - Specification clarifications, implementation notes regarding the C-Intercal compiler, and literature references for those interested in background information on COME FROM and friends.
Catalog of Compilers Intercal Page - Idiom's catalog of free compilers and interpreters mentions Intercal.
Free Online Dictionary of Computing Intercal Page - Short introduction to Intercal, detailing Intercal's distinctivenesses in comparison to other languages.
Intercal "Hello, World" Program - Surprisingly readable chunk of C-Intercal-only source code written by Clemens Meier.
Intercal Programming Language Reference Manual - Original specification.
Intercal Reference Manual - HTML version of the original specification.
Intercal Resource Page - Unofficial Intercal language homepage, maintained by C-Intercal implementor Eric S. Raymond. Documentation, implementations, papers, and tools.
iperl - Using Intercal in Perl.
J-Intercal Project - Intercal-to-Java compiler written by Karsten Sperling. Download, documentation, and links.
Jacob Mandelson's Intercal Page - Featuring a ROT-13 routine and a short link list.
Muppet Lab's Intercal Resources - Features the original specification and an extensive sample source code collection. Links to several compilers and to other Intercal-related sites.
Revised Reference Manual - Compiled from the original specification and from the comments and clarifications by Howell and Raymond.
The Language from Hell - Article and site, non-fiction, and journalism indexes.
The Pit - Intercal source code by Louis Howell.
Threaded Intercal - Malcolm Ryan's proposed standard for Threaded Intercal, version 0.2.