I believe that the search function is not operational at this time, but on the bright side, this site does seem to allow its contents to be indexed by search engines. Hence you can go to google and type in your search term, then append site:http://www.lawschooldiscussion.org and you will be able to get results matching your search from this site.
For example, if you were interested in the LSAT, and the google prompt enter:
LSAT site:http://www.lawschooldiscussion.org
Happy Hunting,