The Scottish Youth Hostels Association
Historic Scotland-they care for many historic properties in Scotland, and if you get a one or two week pass, you can save money.
The Online Guide to Scotland-maps, accomodation, transport, culture, and regions of Scotland.
Touring around Scotland, by Rampant Scotland. This is the best overall site, with over 1200 links to sites for almost anything that you need to know.
The Fort William, Ben Nevis, Glenfinnan, and Mallaig area
The Ordnance Survey-an excellent resource for topographic maps of Scotland.