I've been looking for a long time for a command line tool or sources or an application which can expand multiple rar archives on Mac OS X. And with a single google search, today I've found a Mac OS X port of unrar, unace and binchunker in a package called PC Tools for Mac OS X.
The tools are in a single package form, and the package installs them into /usr/bin. Then, just type from anywhere in the terminal:
% unrar e archive.rarAnd of course, it still works if you have multiple archives attached (.r00, .r01, r02...).
% unace e archive.ace
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020327095725538