Musictheory.net - One of the most important beginner resources. Deals heavily on traditional notation, both reading and writing, and the basics of theory up until Neopolitan Chords. BEGINNER.
Musictechteacher.com - Resources for music theory and music technology, including exercises for learning. BEGINNER.
"The eye that hears, the ear that sees" - A fabulous, complex, if not slightly dry (an unfortunate side-effect of translation) originally French website that explains a complete method for understanding tonal harmony with an analytical mindset. ADVANCED.
"Scales and Modes" - A great site that lists a vast number of scales and modes upon scales, complete with fingering charts and other goodies. In French, but quite usable for English audiences with Google Translate. Via Wayback Machine. INTERMEDIATE.
Philharmonia Orchestra/Explore The Instruments - A good introduction to the range of instruments with video and audio examples. BEGINNER.
Rimsky-Korsakov/Garritan Interactive Orchestration - An excellent must-read for anyone interested in orchestration. Garritan took RK's original manuscript and updated it with contemporary commentary and virtual performances of examples. Unfortunately a little broken, but saved by the Wayback Macine. BEGINNER to INTERMEDIATE.
Indiana State/Instrument Studies for Eyes and Ears - Great introduction with audio examples of all common (and many uncommon) orchestral instruments. A little confusing to dig around (due to outdated Flash construction), but still quite useful. INTERMEDIATE.
Writing for Harp 1; Writing for Harp 2 - Two excellent articles on the matter of writing for harp, one of the "pickiest" (or shall I say, pluckiest) instruments to write for (although don't tell any harpists I said that). INTERMEDIATE.
Contrabass Mania - Although this site primarily deals with JUST HOW AWESOME contrabass instruments are, it has some handy orchestration tips wrapped in a misleadingly web 1.0 format. INTERMEDIATE.
Here at VS, we regularly rely on a broad supply of physical and digital materials and resources to help us in our work. Below is an ongoing sampling of the digital versions of those resources, which we hope will help other composers, young and old.
Beginner: Very basic music theory/general music understanding required.
Intermediate: A solid understanding of theory/gen. music required.
Advanced: Specific interest and a strong understanding of theory required.