If you as me spend a lot of time waiting for C++ projects to rebuild then you generally try to find other things to do while the compiler is generating C02. However it is also very easy to get immersed in your alternate activity, be that reading up on the latest meta programming tricks in boost or consuming noise on slashdot. Before you know it a whole morning has passed but your compile stage finished hours ago.
notify-send to the rescue. When run, it just pops up a subtle message box on your desktop, over all your other windows with whatever message you want. Install it via.
aptitude install libnotify-bin
and then if you are using make
make ; notify-send build done
scons; notify-send build done
ant; notify-send "build done" "you java jockey"