In reply to Dan Arkle:
4 classics spring to mind.
Caingorms. Aviemore/Glenmore In to Corrour. Over to Hutchinson. Down to Faindouran. Out to Glenmore/Tomlintoul. Or in from south to Tarf Hotel then to Corrour. Pretty big days but doable. Over tops or through valleys if weather crap. there are other bothies in the area too.
Ben Alder area. In from Dalwhinnie. Eithier Culra or Ben Alder Lodge. Then all the way over to Fort William or Kinlockleven or Spean Bridge. Bothies at Meanach, Liarig Leacach and another in area. Long distances but used to be a bunkhouse at the rail way stop at Corrour (not to be confused with the bothy! )
Knoydart also good. Private bothy above Glenfinnan, then over to Glen Pean or the one to the north Achuill or simular name. Over to head of loch Nevis, bothy there too. Then out to Inverie, hostel? (boat out) or to Barrisdale, another private bothy then back to Inverie, or the head of Loch Horn (try hitching out on the longest no-through road in Britain?!) or walk.
Theres another classic through from Loch Clunie, near the Clunie Inn. via head of Glen Affric. 3 bothys. One to west of YHA (YHA locked). Bothy called? then big day to another in the middle of nowhere, potential river crossing issues ( i have details on best places to cross the 'rivers'), out to Bearnais bothy to south of Glen Carron.
Cheers Gareth