Back with the feedback.
Perhaps there's more people like me interested in this, so here's my experience:
Once you told me the magic word - normalization - I had no problem finding few programs that do this.
I did download Audacity and I found it to be really broad and with hundreds of options and, honestly, a bit complicated for me. I went for the mp3gain which does only what I need - all songs are equally loud after being treated with this software and it is a 3-4 clicks procedure. Perfect.
One warning from me; this program changes the file and DOES NOT export it, it DOES NOT ask you to save the new version under a different name and so on. It changes the file you point it at and saves the changes 'inside' that very file.
If you have any doubts about it or think that mp3gain will change the playback quality of your file, MAKE A COPY of the file before you process it.
Other than that, I could recommend this program. It is free and I'm listening to the material as I write this, believe me, it sounds almost perfectly set at the same volume level. I deliberately used the files that use to scare me in the past with huge differences in volume.
killdozzer