Olympus E-PM1 has a Micro Four Thirds lens mount and currently there are 94 native lenses available for this mount.
E-PM1 also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on E-PM1.
Since Olympus E-PM1 has a Four Thirds sensor, it has a focal length multiplier of 2× so you have to multiply lenses original focal length with this multiplier to find the Full Frame equivalent focal length of the lens when mounted on E-PM1.
You may also also be interested in these:
Olympus E-PM1 Lenses with Image Stabilization
Olympus E-PM1 Lenses with Weather Sealings