Beginning on May 5, Northwest Airlines joins United, US Air and Delta in charging $25 for a second checked bag each way. As with the other airlines, there are certain exceptions depending on your frequent flyer status and other factors.
Also in the additional fee category, JetBlue is now offering extra legroom at the front of their Airbuses and in exit rows of all their jets (including the Embraer 190) for $10-$20 per flight. Exit rows on JetBlue used to be free on a first come basis, but guess that's history now. But we'd gladly pay the extra for a generous 38 inches of "pitch" (the distance between one point on the seat and the same point on the seat in front or behind). Since many first class seats have about the same amount of legroom, essentially JetBlue has added a "first class" section at the front of the plane, without calling it as such.