switching wireless (ipw2200 on acer laptop) on and off
A problem I often had was this: I would switch off the wireless while using windows to get rid of the annoying blinking light, and after that it would stay switched off in Linux with no way to switch it back on.
There is a way to switch it on from the command line which is so obvious I never thought of it:
iwconfig eth1 power 1
This should be run as root (or with sudo in front of it if you're an ubuntu user). Replace eth1 by the right name if your wireless device has a different name (eg eth0, eth2, wlan...). Use
iwconfig eth1 power 0 to switch off wireless if you would want to do so (to extend battery life maybe?).
Acer laptops (such as mine) have a switch on the front side for switching wireless on and off, but this doesn't work with Linux by default (at least on MY Linux it doesn't). Install acerhk, make sure that both the kernel module and daemon with that name are loaded (if the package manager of your distro doesn't do that for you), and then it will work. Without an annoying blinking light, too.