I'm at the Defense Language Institute (one of the most difficult language schools in the world) for the Air Force right now. Just finished russian. It's not a bad way to go. I was in class with people from every branch except CG, and here's what I've learned:
AF - Good standard of living/Difficult to rank up
If you want to go to college and get your degree, they're more than willing to help. 100% tuition assistance (all the other services have around 75-85%).
Navy - Standard of living ok (living on a ship or sub isn't the greatest)/Rank up easier
They have every job all of the other services have plus some more. Beware of the nuke science program. #1 washout school in the DoD.
Army - Standard of living ok/Rank up easier/Better signing bonuses
If you have outstanding college loans, they'll pay them all off and give you a decent pay grade to start. I have a friend who started out E-4, had $35k in loans repaid, and got a $20k signing bonus. If you have a bachelor's, look to starting out as E-4. If you don't have a degree already, it'd be better to go Air Force.
USMC - If you want to be buffer than [censored], the Marines is for you. Can't really even compare them to the other branches. They're just too different. It's difficult, but doable.
Coast Guard - Keep you close to home, but understand that the Coast Guard sees more action than all the other services. Excellent service if you're looking to go into law enforcement after the military.
Any of them would be a good choice, really. Just depends on what you're looking for. Talk with the recruiters, but don't let them push you into anything. Sigining up with the military is a lot like buying a car. You're in control, remember that. If you hve any questions, email me! I signed my contract Mar 2002, so I am still pretty fresh on it all.