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If you have a significant music library, this program will help locate and attach album covers to your MP3 files. It's a great time saver.

There are a lot of audio editors available on the Internet, many are free, but most suck. Audacity on the other hand is very powerful and flexible audio editor. It's great for recording and editing MP3 files. Of course, like any widely-used application it has plug-ins to make it even more powerful.

It's very difficult to find a free application that will measure the BPM of music in your audio library. This is a useful utility to create playlists based on music speed. It's invaluable for creating the right mix of songs for your workout inspiration.

This is a simple utility for ripping MP3 files from CD's, but still one of the most effective programs for doing so. It's also useful for resampling files to different bitrates, of course that means a bit more loss in the compression, but I suppose that depends on how fussy you are about your collection. Personally, I can't notice the difference between a resampled 128Kbps file and a 192Kbps file, in most cases.

FAE is another excellent audio editor. It's great for cleaning up MP3 files or any form of audio editing you may want to do.