If your in Glencoe then you have to photograph Blackrock cottage..every one does it with Buachaille Etive Mor ( a big pointed mountain ) in the background.Its a left turn off the A82..same turning as for the ski centre.Going on down the A82 towards Glncoe there is a turning left for Loch Etive..just as you go down the road there is a small area to park on the left near a bridge.Park there and cross the road and walk a few yards and you will have a glorious view of a river crashing over rocks with Buachaille Etive Mor in the background..great shot and it is on my site.Loch Etive is lovely..old remains of a wooden pier  ( on my site..maybe in the black and white file ) About a 20 to 30 minute drive from the A82. 
As you go from Glencoe to Fort William after a while you will glimpse a castle in Loch Linnhie.
You go round a bend and up a hill ( still on the A82 ) and there is a cafe on the left...behind the cafe is a parking area where you can walk down a short way to get shots of the castle in the loch.
There is a road where you can drive right around Loch Leven....some nice shots to be had there.There is also a water fall in a little village at the top of the loch at I think Kinlochmore.
Didnt go to it but may be worth a visit if you are up that way.
Kilchurn Castle can be photographed from both sides of the loch..who ever isnt driving needs to look out for a good shot.
Check out the Scotland galleries on this girls site..shes bloody good..got my inspiration for Scotland from her.

http://rebeccacusworth.com/

Eilean Donan Castle is a real stunner.You just park right next to it and get the camera out.Bit of a drive as it is just before you go onto the Isle of Skye on the A87.If you get there shoot it from both sides..some from the car park and some from the long bridge...looks better with the tide up so you may want to check that out if you intend to go there..use the BBC tide and times site.
Eddie