I have used a router jig to make hives. Too time consuming.
I have used the traditional miter gage mounted box joint jig. Works ok, but requires setting up each time you start a batch.
This is the jig I use now. No setup. Just slap it into the slots and start cutting box joints:http://nordykebeefarm.com/forum/forum_posts.asp?TID=18&PN=1