Commutes from DCA to Boston and LaGuardia are a piece of cake. you could use Eagle... but US Air also has express flights that leave every hour! Comair has a good handful of flights too. One of the easiest commutes are far as commutes go.

Last I heard, the Laguardia reserve for new hires is about 8 months. Reserve at Boston is shorter than LGA... around 5-6 months from date of hire. So expect about 3 to 4 months on reserve at Boston once out of training.

The good news is Boston has had a lot of new hires in the last 2 or 3 months (around 20 at Boston alone) so reserve times should continue to drop.

Chicago is really short on pilots apparently, I heard guys are getting lines after a month on reserve in Chicago. Commuting to Chicago though from DCA wont be as easy as BOS and LGA.

Hope this helps.