There is already a good discussion of this topic here: https://community.freescale.com/thread/96370
As far as I can tell, the term PSP (processor support package) is somewhat unique to Freescale (at least I haven't run into the term with other manufacturers). It is primarily focused on a particular processor line and includes code for the core processor and built in modules.
BSP (board support package) is a rather generic industry term and includes the complete system, including external RAM, ROM, IO, and peripherals. You can get a good industry generic definition of BSP at http://en.wikipedia.org/wiki/Board_support_package.
