Some sources for free advanced knitting patterns and instructions include websites like Vintage Craft Patterns, Painting Lilies and Knitting Pattern Central. The Keep on Knitting blog also discusses advanced techniques.
Vintage Craft Patterns offers instructions on creating advanced stitches like the Peacock's Tail pattern and the German Brioche stitch. Painting Lilies offers links to twenty different advanced patterns like lace shawls, a miniature hoodie for an iPhone, and a Celtica jacket. Knitting Pattern Central is a huge directory that includes patterns for everyday advanced knitting items like socks along with decorative items like laces and edgings. Keep on Knitting offers tips on knitting backward or using tools like double pointed needles.