I suggest that you download Amidst v4.3beta2, run it, select a VANILLA profile for the PCMC version you prefer, and start hitting Ctrl-R. (the link is in my signature)
That will cause Amidst to display the biome map of random seeds.
Hint: Place Amidst in it's own folder and create an empty file in that folder named history.txt.
When Amidst starts up it will detect that file and from then on will create a log of every seed that it displays.
That way, if you hit Ctrl-R too quickly you can find out what the seed was of the previous map and redisplay it.
Ctrl-H gives you the seed input dialog.
-970487728449390 plains with xhills on 3 sides at about -800, 1250 however this map also has xhills surrounding 2 seperate forests, a taiga and some other 3 sided plains and various biomes. i found it in mineatlus and have not looked at it in game so i don't know how useful it actually is.