Langton's ant ASCII art.
GolfScript - 67 chars

~17.'_'*n+*\153:|;{|/()[124^.2/6+:6.1&amp;17*)\2&amp;(*|+:|;]@++}*|/();'@'@


hallvabo's Python solution is the most similar to this, so I'll only describe the main differences.

The board is stored as a string instead of an array. This is so we can update a value on the board with less characters (as strings are always flat), and so getting it to the desired output format is easy.

The ant position is incremented by the formula ((d&amp;1)*17+1)*((d&amp;2)-1) (i.e. .1&amp;17*)\2&amp;(*), where d is the direction. We use the variable 6 so we can skip initialization.