I was just playing around with TooManyItems just now, and found out that you can change what the spawner spawns in toomanyitems.txt in the .minecraft folder. The mobs still follow the rules they'd otherwise follow: Animals need grass, monsters need dark, slimes have to be in a slime chunk and in 0-16, etc. You have to reboot minecraft for each change to take effect (say, you can place a pig spawner, close minecraft and edit the .txt, reboot minecraft and place a slime spawner), and the previously-placed spawners will hold to whichever mob they were set to. It should probably be noted that I do NOT have Modloader (it doesn't work at all for me, no idea why, unimportant), but I doubt that would make any difference in this. Anyway, hope it works as well for everyone else. I noticed no one seemed to mention it anywhere, so I figured it might be helpful.
