BBC Learning Music provides online learning, support, and advice for teaching yourself music. It provides courses and videos as well as links to other resources.
Gresham College provides free public lectures that have been given for over 400 years. Includes a guide to subjects and a digital archive of past lectures.
The International Music Score Library Project (IMSLP) is an open collection of the world's public domain music scores and recordings. Search by instrument, difficulty, composer, or time period, and download PDFs of the sheet music. This resource is excellent for initial research of musical composition or simply for a self-training session. All of this website's content is licensed under Creative Commons Attribute-Share Alike.