Released in 1979, the original Sony Walkman completely changed how people listened to music. Your tunes were free to go anywhere — and sound like complete garbage. The quality of music on cassette tapes can't compete to today's digital formats, but if people still like the sound of crackly records, surely there are people who miss the acoustic aesthetics of cassette tape.
Don't waste your time hunting down blank cassettes and broken Walkmans on eBay, however. If you've got a browser and a web connection, a simple site called WebCassette will load and degrade your digital music files so the sound quality hearkens back to a time before compact discs hit the market.
If you're especially particular about how bad your music sounds, the site includes a set of dials letting you adjust the quality of the cassette tape, the quality of the cassette player's motor and the performance of the playback heads.
It will either make you nostalgic for the times you rocked out as a kid in the '80s, or very appreciative of 40 years of personal music player improvements.