Not all composers whose music I would like to be able to share here (or listen to myself) are well represented at the internet archive. But one who is is Jean Sibelius. Here are a few of his more famous works:
Violin Concerto (performed by Jascha Heifetz)
http://www.archive.org/flow/flowplayer.commercial-3.0.5.swf?0.8344390731741345
Symphony No. 5 (Cleveland Orchestra, Artur Rodzinski)
http://www.archive.org/flow/flowplayer.commercial-3.0.5.swf?0.37582674057121407
Finlandia (Cleveland Orchestra, Artur Rodzinski)
http://www.archive.org/flow/flowplayer.commercial-3.0.5.swf?0.3093259739128915