Thanks for the link, Kaisha, that was still helpful. That, and some more google-fu, turned up the answer. Posting it here for future reference. You now do &include=a,b,c ... where "a", "b" and "c" are the forum ID numbers you want to pull from. Here's the code that will search all the FFXIV forums for new posts:
Code:
http://www.bluegartr.com/search.php?do=getnew&contenttype=vBForum_Post&include=121,92,131,133,128,130,122
... and getnew can be replaced by getdaily if you want to see what else has been active recently:
Code:
http://www.bluegartr.com/search.php?do=getdaily&contenttype=vBForum_Post&include=121,92,131,133,128,130,122