I have attended only one code camp and that was part of my cs studies at the university. It was great fun as it took over the whole weekend and it was sponsored by local companies providing pizza and drinks. We learnt about location based mobile applications and we put together some simple games using user's location.
What kind of experiences you have had during studies or after graduation with code camps?
Code Camp was one the best "micro" conferences I have ever been to. I think a lot of it depends on the quality of the local presenters that they recruit, but we covered a lot of LINQ and ASP.NET MVC at the one that I attended (a little over a year ago). It was easily as much or more value per unit time invested as TechEd -- though TechEd covered far more topics and in much more depth. Much better value, IMO, than any conference put on by one of the "conference companies" that I've attended.
I've been to a couple of Code camps here in Calgary and would say that they are awesome. In both cases, there were multiple tracks and it seemed like a good way to see some developers in action as well as see what kind of laptops people had around, e.g. VoodooPC, Dell, Toshiba, Mac, HP, etc. There is the seeing of the code as well as knowing that this isn't dozens of hours of work distilled into a few screens showing that "This is how you..." presentations that seem to be pretty common for the Microsoft events here.