Buses for the highlands from Glasgow or Edinburgh - try Stagecoach site for timetables. You can book online or by calling the bus station - Buchanan bus st. for Glasgow or St. Andrew's for Edin.

There are also local buses in most areas giving a good service until early evening. You'd need to look for online timetables for services in the area you are visiting.

Curious at to where Rabbies go that you cannot get to by public transportation? that is where a tourist with limited time cannot get to?

Yes -- you <i>can</i> get to many places by public transport -- but the rural areas/sites covered by most Rabbies tours -- there are very few buses, like once or twice per day. So to get someplace Rabbies takes you and have a couple of hours to explore before moving on to the next . . . would take two days to accomplish on your own.

I suspect lots of rural sights would be difficult to reach by public transport. Neist Point, for instance:
http://www.walkhighlands.co.uk/skye/neistpoint.shtml

If you are really interested in hill walking and some climbing, consider going to the Isle of Arran. An hour on the train from Glasgow takes you to Ardrossan where you catch the ferry for a 55 minute sail to Brodick. The are are loads of bed and breakfast places there for an overnight stay. Look up the island on the web. It is an outstanding area and is considered to be Scotland in miniature.