I've broken network-manager trying to compile it from source, the applet no longer shows in the panel and I can't connect to any of my (wireless) networks. How might I restore it? I've tried reinstalling the network-manager packages from main repository but had no luck recreating the applet icon/indicator.
I had a similar problem. A short-cut to get it working again is to just use Wicd - http://www.wicd.net/ - which is an alternative to network manager.
The other way is to restore network manager from the repository again. Run
sudo make uninstall and delete any network manager libraries,
apt-get --purge remove network-manager (and any other packages), and re-install all the packages, and gnome-networkmanager.
Also, running nm-applet from within the terminal might generate some more useful debugging information - primarily identifying whether the applet could create a d-bus connection to the network manager.