Here are some classical MIDI files for your enjoyment. 

The files are in SMF (standard MIDI format), some are General Midi, but others are for specific synths, so you may have to tweak patches on those. 

Click on the file name to go to the midi file -- with an appropriate helper app you may be able to play it. Otherwise, with browsers such as Netscape you can SHIFT+CLICK on the name to download it to your disk and play it later on your sound card or synth. The file size is provided to give you an idea of the length.