FYI-
Lee Valley tools has router bits for birdsmouth joints (6,8,12,or16 sided). I don't know if they are easier than setting up a table saw, but thought I would pass the info on. Let me know if they work.
Here (i hope this works) is the link. If not, go to www.leevalley.com and search under "birdsmouth" and you'll find it.
http://www.leevalley.com/wood/page.asp?SID=&ccurrency=2&page=45160&category=1,46168,46174
P.S. I have no affiliation with lee valley (or birdsmouths)