I use Ubuntu on my laptop at BigBlueHat almost exclusively (save for some Photoshopping). I ran into a problem last week with having the same IP address as our wireless printer. After some man page research, I can up with this solution:sudo ifconfig eth1 address 192.168.1.7
For me, that changes my wireless card (eth1) to use 192.168.1.7 IP address. The really happy part was that there was no rebooting required, and the changes was quick and painless though a bit geeky.