Audacity is a beauty of an open-source (free) software. Not only is it a sound editor for those who are into editing and mixing digital sound files, it can also do a couple of interesting things:
1) Record streaming music on the Internet. There are quite a few legal streaming music sites online, and I've always wondered how the streamed music can be recorded into my hard disk; well, with Audacity I can. In fact, on the Audacity website it provides a detailed how-to. Here is an example of a music clip recorded from the Internet radio service on Yahoo.
2) Record whatever sound that is produced on the sound card inside your computer, such as by playing your CD or DVD collection -- just set the input source to "Wave Out" and hit the "Record" button; when the recording is done, click on "Export as MP3" to convert the recorded file into the MP3 format. This process is different from "ripping", which Audacity does not do. Here is an example of a music clip recorded from my own CD collection.