hi Greig, as Alan says, where do I start? Did part of it last year, and favourite campsites were Big Sand at Gairloch, and Clachtoll, both right beside a beach. A walk up Stac Pollaidh (think that's the spelling) is a must, even if you're not normally into hillwalking - strange rock formations and amazing views on a clear day, and it doesn't take that long to walk up. Then the single track road from there to Lochinver (instead of going back to the main NC500 road) makes for an interesting drive.
Loads of other stuff to see and do - check out the NC500 website, take your time and stop to explore when you see anything interesting, Alan