Well for the 10,000 for $100 promo (looks like it's only valid for the Signature card) you can go to this page on NW's site: http://www.nwa.com/100savings/

There are also bonuses right now (200 points) with the Miles to Go promo for signing up for a NW card if you don't have one already.

Direct link for the sign-up page thru Miles to Go promo: http://www.worldperksvisa.com/wpv74