You will need an MP3 Shield of some kind to do the decode. Google can help there.
Since you talk about a browser you will also need some kind of network access. That can be an Ethernet Shield if you have an Ethernet outlet handy. The Ethernet Shield also has an SD (or Micro-SD) car slot for file storage.
If you need to use a USB Thumb Drive instead of an SD card you will need something like a USB Host Shield.
Once you add all this additional hardware you might be better off getting something like the DUE or even the RaspberryPie.
I found several MP3 shields, this
one for example has an USB-port. The point is that I can't find any tutorials/example code on how to create a proper media player that allows me to play a certain file instead of skipping through all files (any suggestion as to where I can find this information?)
I got an ethernet shield, so that shouldn't be the problem... Once I know how to play a specific file it won't be too much work to do that by user input through the browser...
Let's say I got a 3 mp3 files on a thumbdrive connected to the music shield: CrossRoads.mp3, johnwasser.mp3 and niellles.mp3. I'd like to write a code that can do something like this:
play(c) (where c is the filename)
Instead of all the examples that I found so far where the files would be named : 001CrossRoads.mp3, 002johnwasser.mp3 and 003niellles.mp3. Arduino would start playing at 001CrossRoads.mp3 and I can only skip through the files.
As I said; I'm pretty new to this stuff so I hope that you guys understand what I'm trying to say...
I thought about the RaspberryPie but that doesn't seem the best solution. Do you mean the Arduino Due with "Due"? What would be the advantages of this board?