If it was me I would probably use an ADSI script or look into something like ldife utility that you get from microsoft. You use or used to use the ldife utility on one of the MS courses.
I would probably go for an ADSI script personally. I have the book with all the field names in if you want any they are hard to find otherwise.
Look at some of the programs touted for bulk adding of users as well though as they might have some features you want.