So you probably know you can climb Mount Everest (that is, if you're in fantastic shape and you have the funds and the drive); but until recently, I didn't know you could do this base camp trek. A friend of mine's son is going there soon.
You can go either to a north base camp (via Tibet) or south (via Nepal). You may scoff at heading to base camp only; but check out the itinerary. Wowza.