Professional Organizations for Composers:
Performing Rights Agencies
Research & Advocacy
This website is a reference for information on every orchestral instrument (plus many others) as well as the sections as a whole. It utilizes audio and video for reference, as well as print.
Features handy software tools, (like calculators for matrices, prime forms, pitch relationships, etc.), as well as tutorials on 20th cen. theory techniques.
Features a blog, as well as tips and videos.
Fingering charts and fonts
Cover letter writing guide - music specific