Back in college, we had this huge LAN spanning hundreds of computers, and we had a central instance of a search engine that crawled all the Samba and FTP shares, so anyone could just look up whatever media or software they were looking for, and if the particular computer was online at the time (people do turn off their PCs sometimes, go figure :) ), download it.
Of course, I'm not sure if having unprotected SMB/FTP shares is something fitting into your idea of a local intranet, but it's an option. The guys maintaining the crawler even put the code online, and it should still mostly work: https://github.com/fslts/lase