In addition to the many fine commercially available textbooks for music survey course and fine music encyclopedias behind the paywall (Oxford, and others), the resources below provide free and/or open overview of typical music survey course content.
Online Resources

History of Western Music (Naxos)
Brief overviews and timeline of western classical music history with lists of typical or major works for each era. Music links to Naxos catalog (behind paywall). Links to music in the Naxos catalog are behind the paywall, but accessible through many libraries.
Video Resources
Period music (Nicholas McGegan)
Learning to Identify the Western Orchestral Instruments

LSO – London Symphony Orchestra (UK)
Interactive Symphony performances. Excellent resource, but requires a good internet connection. At home page, Click “Select a performance” to begin instructions.

Perfect Pitch
Interactive overview of instruments of the orchestra from Baroque to modern times. Appropriate for all ages (children through adult). Interactive introduction to the orchestra and instruments across history, using baseball metaphors.

Philharmonia Instrument Videos
Information and videos on individual orchestral instruments.

Carnival of the Animals (Saint-Saëns)
This Wikipedia link lists and describes the 14 movements of this piece also listing which instruments are playing each movement, and describing the musical jokes in the music. Many audio and video-recordings of this music are available, none designated as open source at this time.
Peter and the Wolf (Prokofiev)
Many audio and video-recordings of this music, none designated as open source at this time. Some narrations specifically describe and name the instruments being played. Others do not. Introduction to the concept of “leit motif” and featuring specific instruments of the orchestra. Often programmed at children’s concerts as an introduction to the orchestra.
Young Person’s Guide to the Orchestra by Britten
This Wikipedia link lists and describes the movements of this piece also listing which instruments are featured in each movement. Many audio and video-recordings of this music are available, although none designated as open source at this time. This piece features specific instruments, but does not isolate specific instruments and instrument families as clearly as the other sites listed above.