Microsoft provides free training events in the form of dev camps. One such dev camp is Windows 8 Developer Camp. Windows 8 Developer Camps are free, fun, no-fluff events for developers, by developers. You learn from experts in a low-key, interactive way and then get hands-on time to apply what you’ve learned.

If you don’t have the time or ability to attend these events in person, you can still benefit from them by downloading the Windows 8 Camp in a Box. There are two versions available: C# and JavaScript.

You can get it here:

http://www.microsoft.com/en-us/download/details.aspx?id=29854