Scott Sutherland's " Generalized Ants" is my favorite overall page on Langton's Ant, with a good list of links, references and software. Scott is one of the authors of:
D. Gale, J. Propp, S. Sutherland, and S. Troubetzkoy
"Further Travels with my Ant"
Mathematical Intelligencer 17 (Summer 1995), pp. 48-56
This includes references to some earlier articles by Gale and Propp.
Jim Propp has moved from MIT to the University of Wisconsin at Madison. Some Vant software is available from his page.
Jack Cohen and Ian Stewart have written books together including The Collapse of Chaos. Both have written about Vants:
Ian Stewart wrote an article about Langton's Ant in the Scientific American, July 1994.
The Critical Rationalist, v2, #3 is an article by Jack Cohen:
" 3 Reductionist Nightmares, Game Trees and Ant Country"
Ronny Ziegler and Fabian Kühne wrote a paper. "The aim of our research was the description of a cellular automata, which is a combination of two Langton's ants. This automata shows special symmetries and rules, which we wanted to find and describe." Includes an applet right on the table of contents page.
firstname.lastname@example.org has an Ant program for Unix. (Matt seems to be theory.org).
Anna Claudia Nardella wrote a Java Vant that seems to be referred to everywhere.
Page has some Vant stuff.
Bill Casselman has written a Java version of Langton's Ant.(dead link?)
Jeff Steidl has Ant program for Windows, and some links.
Janne Blomqvist has an applet with multiple ants in color following different rules!
Peter A. Wentworth's applet has multiple rule-2 ants in different colors.
Matt Wilder has an applet.
alife.co.uk ...Look under "Ants" for 3 or 4 applets & links.
Nubz.org's products page includes a programmable Vant Screensaver for the Mac.
Michael Ranner offers an Amiga program with source.
Michael Rosander has a RealBasic Ant program