Spanish PS2/PS3 Developer ifcaro has updated his PkgView application, this app allows for the viewing and extraction of one or all contents of a PKG file, here is a quote from the changelog:
FIX: PARAM.SFO doesn’t appear
FIX: Emprty folders doesn’t appear
Add support for retail pkg (thanks to Mathieulh’s app).
Now accepts pkg files passed as parameter.
Added support to drag pkg files to the application.
Added Extract to source folder option
Added .pkg file association
Added Extract here at Windows’ contextual menu
A video of it in action: