Ah yes, we use mainly mac's here but now have vague recollections now of the old 150's being cranked up to 166? - that would have been over a decade ago?
And yip, it's a dual 168 / dual chip / dual IC / dual socket, but we're going to call it our "Dual Core 168" because it sounds cooler.
Applications, ummmm - dunno really, we're only using it for [ serial --> master --> slave <---> serial ] so in that regard, it's an inexpensive plug-in solution for adding a second serial buffer, which means we're not having to wrestle with software serial anymore, nor do we need to use a wiring board which solves the same problem, but is bulky and costs a lot. We've had one of those here gathering dust for over 3 months, but we like this idea better because it uses a lot less real estate.
The no-frills design is an elaboration of this:-
http://art364.pbwiki.com/Standalone+Arduino
And Paul Badgers RBBB design.