If you have a mp3 (or FLAC) based music collection:
Write a file backup or sync program. Compare the contents of two directories and only backup files that are new or different.
Write a GUI that offers all the options to a user (source and destination directories, pattern to match files and/or dirs, copy option flags, etc). Allow some sets of options to be canned and run as a macro.
Extend the comparison to include ID3 tags. Use that to sync your music collection across multiple devices. Add flags to copy all files or new(er) files, to copy empty directories or not, to remove files in the destination that are not in the source (or not).
Extend the tool to ignore (or fix) tags that differ only by whitespace or capitalization issues.
Extend the tool again to find duplicate music files by comparing ID3 tags and filenames - allow for matches that ignore "A", "The", etc (e.g. "The Beatles" and "Beatles" are the same band).
Extend the tool again to fetch missing ID3 tags from freedb (or amazon, or somewhere else) and update the songs. Have a way to reconcile the tags between different devices by only updating the tags, not copying the whole file.
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