A simple task I typically forget is how to list IP addresses on a network. This can come in handy if you forget what IP your server is on or if you need to check what all IPs are up. As Admins eHow shows, the command is simple if you have nmap:
$ nmap -sP 192.168.1.0/24
Or, you can do a range:
$ nmap -sP 192.168.1.0-10
Now, let's say you need to check if a port is open, you can do that too using nmap:
$ nmap -sF -p22 192.168.41.0/24
There are many other fun things you can do with nmap too, see my full article at http://thesimplesynthesis.com/article/nmap/.