I saw this older hint about getting the "human readable" version of information from the df and du commands. As of Panther, at least, the du, df and ls commands all take the -h option. Not only is it no longer necessary to tweak your du or df command to get the behavior, but I think this feature in ls is relatively recent, too.
As far as I can tell, Mac OS did not adopt the GNU fileutils, but they did adopt this nice feature. I find it handy when I'm using a Terminal to use ls -lh, so I don't have to count digits to figure out the sizes. Here's an example:
% ls -lh
total 5504344
-rw-rw-r-- 1 paco staff 42B 3 Aug 20:59 01.gif
-rw-rw-r-- 1 paco staff 872M 3 Aug 22:43 BTV Movie 001.mov
-rw-rw-r-- 1 paco staff 1G 3 Aug 22:47 BTV Movie 002.mov
-rw-rw-r-- 1 paco staff 2M 30 Jul 14:54 GameServices.pdf
-rw-rw-r-- 1 paco staff 1M 3 Aug 17:29 befw11s4_v4_ug.pdf
-rw-r--r-- 1 paco staff 460B 3 Aug 16:58 chiras1-nt
[robg adds: If you use the -h option a lot, you might want to create an alias for it -- I use lsh, which is an alias for ls -alh, the options I use most often with ls.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040804000029326