United has now joined American in charging $15 for the first checked bag. Look for the other dominos to fall this week.
In other fee news, the guys at FareCompare (who are even more nuts about the minutia of the airline industry that you and I are), have created a full list of every fee the airlines are charging, plus all of the various free & pay food options. You really do have to take these additional fees into account when you book your flight, as they vary immensely. (Thanks to Upgrade Travel Better for the heads up).