The FBO on the field is Energy Aviation, +1 (570) 368-2651. The FBO is on the West Ramp. Operating hours are 0630-2100 LCL. After-hours fuel by prior arrangement. Mechanics are available. Charter and catering services are available by calling the FBO.
Cloud 9 Restaurant, located on the East Ramp it the main terminal building, opened in the spring of 2012. Telephone: +1 (570) 601-4603. Aircraft parking is sometimes allowed on the east side of the control tower.
Energy Aviation (see above) rents aircraft and has several flight instructors on staff.
There are several other CFIs in Williamsport, at least half a dozen, probably a dozen or more. I'll add them to a list here as soon as they give me their preferred contact info.
You can learn to fly Light Sport aircraft at AvSport of Lock Haven. LSA rentals and maintenance available.
If you are located near Selinsgrove, check out Heritage Aviation.