Can't listen to MP3 files in Chromium? Here's an easy fix.
Alas, this is one of the differences between the open source Chromium browser and its semi-closed brother, Google Chrome. Many of the audio and video codecs included in Chrome aren't included in Chromium due to licensing, patents -- all that fun stuff.
Fortunately, there's a workaround -- and it's pretty dang simple. All you have to do is copy over the official Google Chrome audio/video components and paste them into your Chromium browser's folder.
If you don't have both Chrome and Chromium installed, you'll need them. Grab a dev channel version of Chrome if you need to, as it's the closest thing to a Chromium snapshot build.
You're looking for three files: avcodec-52.dll, avformat-52.dll, and avutil-50.dll. They'll be located in your Chrome\Application folder (somewhere like C:\Users\You\AppData\Local\Google\Chrome\Application\6.0.437.3).
You can get to them pretty quickly by going to start > run > %localappdata% [enter] and then drilling down.
Copy the files and then paste them into your Chromium\Application folder(e.g. C:\Users\Lee\AppData\Local\Chromium\Application\6.0.442.0).
I'm running Ubuntu, so your folder locations may differ depending on your distro of choice. The file you're after is libffmpegsumo.so and it's located in /opt/google/chrome on Ubuntu.
Head to your Applications folder and right-click Google Chrome. Choose show package contents and drill down to Versions > Most recent # > Framework > Libraries. Copy libffmpegsumo.dylib.
Now find your Chromium icon. Again, right click and choose show package contents and drill down to the corresponding location. When you see libffmpegsumo.dylib, paste and click replace when prompted.
If everything went as it should, you can now enjoy MP3 files (as well as some additional video formats). Now if you'll excuse me, I'm off to listen to my ExtensionFM library in the latest Chromium snapshot build...