Open Source & Free Audio Software & Plug-Ins for Mac OS X

I use open-source software all the time outside of my studio work, but I still turn to trusty Logic Pro for sequencing/DAW. However it's perfectly possible to go Open Source or Free (as in Beer) in the studio too these days. Easier on the wallet, and no need to go down the dodgy crack route... Here's a list of some stuff I've tried out, some of which I use regularly in my own productions and remixes. It's mostly OS X, since that's what I use for production personally, but most of these have Linux or Windows versions too...

Audio Editing
Audacity
http://audacity.sourceforge.net/
Very decent open-source audio editor.

Switch
http://www.nch.com.au/switch/mp3.html
Batch converter for WAV/AIFs/mp3s. Essential little tool.

Sequencers/DAWs
Ardour
http://ardour.org/
A full featured Open Source DAW/Sequencer. You need to pay a minimum of 1$ (more if you're feeling flush) to get the full version which allows you to load and save Audio Unit settings.

Reaper
http://reaper.fm/
Not really Free nor Open Source, but I'm including this here because it's very reasonably priced (60 US$ at time of writing) and because it allows you to download a full uncrippled version for evaluation purposes. It's also a little less quirky than Ardour, especially if like me you're more used to Logic/Cubase rather than Pro Tools, and it is a more than worthy substitute for those more expensive offerings.

Plug-Ins
Smart Electronix
http://www.smartelectronix.com/
A loose collective of developers dabbling in music software. Some great off-the-wall plugins and more trad stuff too. Including mda, Bram, DestroyFX and others...

Togu Audio Line (TAL)
http://kunz.corrupt.ch
Loads of wicked free plug-ins. Brilliant sound, I use these a lot.

Audio Damage
http://www.audiodamage.com/downloads/
Commercial company that also do some free downloads, a vintage Compressor, Pulse Modulator and Fuzzbox

Izotope Vinyl
http://www.izotope.com/products/audio/vinyl/
Great novelty plug-in, make your tune sound like it's on an old worn-out '78rpm disc :-)

Alphakanal Automat
http://blog.alphakanal.de/
The awesome (and free) Automat soft synth.

CamelAudio CamelCrusher
http://www.camelaudio.com/camelcrusher.php
Nice distortion/compression/filter combo available for free download.

Studio Toolz (http://www.studiotoolz.net) is an online resource for free Mac Audio software and is worth checking out.

If you want to try out a full operating system geared to audio, you could try Ubuntu Studio, a distribution of Ubuntu aimed at multimedia creation: http://ubuntustudio.org/. It includes Ardour, Audacity and other Open Source tools. I can't vouch for it, since I haven't tried it, but it seems like it's worth a look.

Happy downloading :-)