International Music Score Library Project (IMSLP) / Petrucci Music Library. Tons of music scores are now
available at this site. If you're a musician, and need an instant pick-me-up, then go visit this site. It is loaded with goodies, including material from the SCA Period.
Numerous facsimile copies of period music are now available from the IMSLP site - its a great place to start researching. Pick a composer, and enjoy!