What desktop environment/window manager are you using? I'm using fluxbox and in order for me to hear sounds in firefox I have to start firefox with the command aoss firefox. If you are using KDE or gnome you may have to use their sound systems. For instance I think in KDE you have to use artsd.
Which plugins aren't working? If you use firefox post the output of this command (your firefox path may be different):
ls -l /usr/lib/mozilla/plugins
When you say you can't "access the compiler globally" do you mean you can't run gcc as a standard user? And what distro are you running (you should set your profile accordingly)?