During 2013 Syncfusion have been releasing additional books in the series of Succintly. They cover a lot of development areas and are all free (PDFs).
Per se it’s not free as You need to pay $ 1 for 1 license which is also valid for next offer.
Another offer for Hobbyist is the Essential Studio for WinRT (Windows 8.1)
Anyway, I find it nice when a company like Syncfusion actually see the group of hobbyists.
Yes, I’m a full member of the Hobbyists group 😉