Anyone know if there is a program similar to the BiG World Project that works for Icewind Dale?
There is IWDTutu
and it implements IWD 1 in the IWD 2 engine. That also means it updates the game for 3rd Edition D&D, which is a HUGE change!
Existing mods won't work for it, but once it comes out of beta we might see some conversions. That said, getting out of beta may take a long while, yet! Development seems to have stalled.
It's not quite what you were looking for, but it's a step in that direction. We may never see anything actually analogous to The Big World though.
Thank's for the heads-up, I'll check that out.