A sound-file editor with multitrack capabilities. I use it for volume adjustments, fades, etc., but it seems designed as a serious tool for electronic composition and recording.

Quickly chop up an Mp3, alter volume, add a fade-out, etc. Works directly on the Mp3 file so it is fast and "lossless."

Adjusts the volume of Mp3 files. It analyses average volume, not just the loudest point, for more practical results (though such an approach could easily distort a particularly dynamic piece of classical music.) It can work through a list of files and set them to a uniform volume, and it works directly on the Mp3 code so it is "lossless."

A nice standalone tag editor. Can shape up a folder of mp3s very quickly.

Speeds music up, slows it down, can attempt to "kareoke" it by knocking out the parts balanced in the center.

Quickly encode .WAV files to Mp3 using the free LAME codec. A little difficult to configure, at first, and you have to install the lame .dll. But, once you've got it, fast, trouble-free encoding is just a few clicks away.

Renders MIDI files as WAVs, and, as the title implies, can use a varied palette of synthfonts (collected waveforms and samples) to do it.

Another MIDI->WAV program. I actually never got this one to work, went back to synthfont instead. Some people do recommend it, though, difficult configuration notwithstanding.

I tried a few different free MIDI sequencing programs over the years, but they were all too primitive and unstable. This one is great for recording and editing MIDI, and it does multi-track audio as well. It is quite stable and reliable, and I'm impressed by how much it offers for such a low price (about $40).

A free program for music notation, intended to get you hooked on the expensive and complicated Finale.

A dopey tap metronome that I wrote.

A simple, automated tempo analyzer - drag and drop a file and it will calculate the BPM. It is, of course, not 100% accurate.

For recording from "line in" jack or external microphone - this application can sock it away to compressed Mp3 files, thus allowing you to record a lot longer.

A collaborative effort that boasts thousands of titles. Conforms to Canadian copyright laws.

John Mamoun scanned a bunch of public-domain editions of piano music, and he offers them here in PDF form.

Another collection of free sheet music - these editions seem to be newly created by many different people.

Pierre Schwob's massive collection of classical music MIDIs and MP3s. I suspect that most people don't realize how useful MIDIs can be for a quick reference - lacking a recording at hand, this is a quick way to hear what something sounds like.

A download service that sells independent music (i.e. stuff on the smaller labels) for about .30 per track in a plain Mp3 format (so no annoying use restrictions). I don't want to seem like I'm shilling, but I do highly recommend it for anyone who studies music.

This site indexes free classical recordings on the internet. It's an ugly-looking site, and a lot of the recordings are terrible, but if you are patient you can pick through and find decent, useful things.

Extensive listings of free and fee-based music software. A mix of useful stuff and junk.

An open source music project for scores and recordings.

These scores are all set using lilypond.