Keep an eye out at Tron Kirk — you're likely to discover some treasure or trinket in one of its many stalls. After you've had a good look at the wares, try some fare from one of the food vendors.
You'll have sightseeing choices galore when visiting Old Town Edinburgh. Tron Kirk is a great place to start here, but there are lots of other fine spots to discover. Edinburgh Castle, Murrayfield Stadium, and Edinburgh Playhouse Theatre are not far from the community marketplace and will fill in your day nicely.