This is somewhat controversial. Some feel that a quality lens should not require further software correction. In fact, the lack of geometric distortion is a traditional sign of a high quality lens.
I think that this is mostly a non-issue. By allowing some aspects of the image to be adjusted in software, the lens designers can focus on issues which cannot be corrected in post processing. This has the potential of making the lenses better, at a smaller size, and potentially a smaller cost. Panasonic Micro Four Thirds lenses are adjusted for geometric distortion and some chromatic aberrations. The geometric distortion is also corrected in Olympus Micro Four Thirds cameras. At this time, though, Olympus does not correct chromatic aberrations.
To illustrate the geometric distortion done with various lenses, I have photographed a tiled wall with them, and shown the sensor output compared with the corrected JPEG output.
Here is an example pair from the Lumix G 20mm f/1.7 pancake lens:
uncorrected RAW output
Note that this is in no way a criticism of using RAW images. There are many RAW image converters which will do the distortion correction automatically and seamlessly, and you will never notice that there was any geometric adjustment done at all. I am using the RAW images to visualize the initial image captured by the sensor, as it is the only way to access it.
Here is a comparison of the uncorrected and corrected images for some lenses. Since I am only interested in the geometric distortion, I have increased the contrast so that the images become monochrome. I also superimposed the corrected out of camera images (black) onto the original uncorrected images (red).
I have also included the appropriate adjustment needed. The adjustment numbers in percent refers to the "Lens Distortion" filter in The Gimp.
Lumix G 20mm f/1.7: -11%
Lumix G 14mm f/2.5: -16%
Lumix G 14-42mm f/3.5-5.6 @ 14mm: -18%
Lumix G 14-42mm f/3.5-5.6 @ 30mm: 0%
Lumix G 14-140mm f/4-5.8 @ 14mm: -17%
Lumix G 14-140mm f/4-5.8 @ 30mm: -4%
Lumix G 45-200mm f/4-5.6 @ 45mm: +1%
Normal zoom lenses pretty consistently feature barrel distortion in the wide end. The tele zoom Lumix G 45-200mm appears to have some very small pincushion distortion, but very minor.
Some lenses that do not feature any geometric distortion correction are the Lumix 8mm f/3.5 fisheye and Panasonic Leica Lumix DG Macro-Elmarit 45mm f/2.8 1:1 Macro lens.