In reply to AntonSC:
Another vote for Coire Lagan. There are plenty of flat spots by the lochan and it's an idyllic spot. I'm pretty sure by the lochan in Coir a Ghrunnda would be very nice too but I don't remember how much flat grass there is to camp on there... it's a bit rockier.
I'd definitely suggest not camping anywhere close to the campsite (doesn't sound like this is what you would be doing anyway though).
Also second the parking issue, it's very limited in from of the campsite entrance and right now Skye is _BUSY_. I drove into Portree today and it felt like the middle of Edinburgh. There was a queue of traffic about a mile long waiting to get through the centre at one point. If you pick a location that isn't a known place to visit, you'll be fine but if you are trying to park somewhere popular then either arrive very early or pretty late.
Post edited at 22:54