I know bus tours ain't everyone's cup of tea but I really enjoyed a day trip bus tour from John O' Groats to Orkney many moons ago.

For £74 I think this is good - day trip to Orkney from Inverness (easy to get to) and back. Nice scenery on the way up to John O' Groats, ferry to Orkney and visits Skara Brae, the Ring of Brodgar and the Italian Chapel (all must sees imo).

http://www.jogferry.co.uk/getdoc/e6ba3c39-e306-48e1-b33c-c0127e3546f8/Inverness.aspx