Here are some links to websites with information (or more links) related to Schubert.
1. Cynthia Cyrus's cleanly done, concise, and very helpful Schubert links. Cyrus is an associate dean and associate professor at Vanderbilt. She is a medievalist and apparently also a Schubert fan.
2. Schubert-Autographe. A remarkable "online databank" of Schubert autograph manuscripts in Viennese holdings. An ongoing project of the Wiener Wissenschafts-, Forschungs- und Technologiefonds (WWTF) in collaboration with the Institut für Angewandte Musikwissenschaft und Psychologie in Köln (IAMP) and the Musikwissenschaftliches Institut der Universität Wien. If you click on the button "Über Schubert," you'll reach a short biography and, at the bottom of the page, a set of links to the New Schubert Edition, Schubert societies in several countries, works-lists, and festivals. As is so often true of links-lists, some but not all are current.
3. The same, alas, is true of links provided on the Schubert-Edition site: links. Scroll down to "Schubert Im Internet" for sites specific to the composer. But that's the Net....
4. Continuing the theme, here's a link to the Schubert Society of the USA, a NYC-centered group whose activities and web-site are apparently undergoing change at present.
5.-6. The Wikipedia article on Schubert is quite decent, though it whitewashes a number of aspects of Schubert's life and personality (that is, it reads like something Schubert's agent would have written). The article has links not included on the sites named above. My personal favorite is the collection of digitized cylinder recordings from the University of California at Santa Barbara. Several performances of the Serenade are on offer, but also characteristic waltz "suites" recorded in 1913 by the České Trio z Prahy and in 1909 by the Indestructible Military Band (!). I haven't been able to verify yet that the pieces are actually by Schubert but will work on it. Unfortunately, the item listed as a "valse sentimentale" has not been digitized.
7. Tomoko Yamamoto's wonderful photo-biography is a treat: Schubert-Project. Like any good travelogue photo-set, it makes me want to repeat her journey.
8. Finally, a link to a performance of D779n31 (not 13) on alto viol, no less, and guitar: Ernst Stolze. There are, of course, many performances of Schubert waltzes on YouTube -- I'm afraid I just don't have the patience to wade through the morass of student performances, bad audio, and/or bad video to find the handful of adequate video files that are undoubtedly there somewhere.