I'm not too fussed about the likes of forestry (although the cutting down whole trees instead of blocks is nice, I'll admit) particularly since it'll need artificial spawning to get it working. Next map, maybe.
However, a BC/IC crossover mod would be very nice...
Something like:
http://www.minecraftforum.net/topic/...2-195b-sspsmp/
It would also remove the potential Peak Oil problem we're going to have.
Oh...and..well..
http://www.minecraftforum.net/topic/...ppelin-mod168/