Reverse Boustrophedon Text
Bash + GNU utilities, 204



fold -$1|sed 2~2{s/.\\+/printf\ %$1's "`echo "&amp;"|rev`"/e
y/'`printf %s {A..Z} {a..z}`"&amp;_?!\"'.,/∀qƆpƎℲפHIſʞ˥WNOԀQɹS┴∩ΛMX⅄Zɐqɔpǝɟƃɥᴉɾʞlɯuodbɹsʇnʌʍxʎz⅋‾¿¡„,˙'/
}"


N is given on the command line and S is given via STDIN:

$ echo "The quick brown fox jumps over the lazy dog." | ./boustrophedon.sh 30
The quick brown fox jumps over
                ˙ƃop ʎzɐl ǝɥʇ 
$ 


Explanation


fold -N splits the input into lines of length N.
The rest of the processing is done by sed, line-by-line:


2~2 matches every other line, starting at line 2
s/.+/printf %'N's "`echo "&amp;"|rev`"/e uses GNU Sed's exec feature to call a shell to reverse the line and left-pad it with up to N spaces
y/ABC.../∀qƆ.../ transform characters



Note ABC... is generated using a bash expansion and printf.  Also some fancy quoting for all the different characters.