the Marshals Service
The personnel functioning as baliffs in Federal Court are called COURT SECURITY OFFICERS and are not full fledged U.S. Marshals. There are about a dozen that work at the local Federal Court house. They are armed, and are all retired police officers or deputies or state troopers.
Many federal court houses also have armed uniformed security personnel for security of the facility. They are usually contract employees and are actually employed by Wackenhut or one of the larger private firms.
I know a couple of the local US Marshals slightly, mostly from attending training with them or bumping into them at the range. They've told me that the best job in the Marshals Service is doing fugitive apprehensions. (It's not as cool as being Tommy Lee Jones in THE FUGITIVE but it's pretty good)
They do have a program where they hire MPs & SPs right off active duty. The younger brother of one of our dispatchers was accepted and then had to drop out because he got his crazy girlfriend pregnant, and now he works in a liquor store and as a pizza delivery guy and battles her about visitation rights. A bad ending to that story . . . his whole life plan got derailed.
Another one of our dispatchers is waiting for the USMS to start a hiring process, which may happen in 2006. He has a double major in Political Science and Spanish with a minor in criminal justice, so I would think he would be an attractive candidate.