Probably le best way is to use NMAP (http://nmap.org/) in ARP Ping scan mode. The usage will be something like nmap -sP -PR 192.168.0.* (or whatever votre network is). The command is nmap -sn 192.168.0.* in newer version of nmap.
The advantage of this approach is that it uses le Address Resolution Protocol to detect si IP addresses are assigned to machines. Any machine that wants to be found on a network needs to answer le ARP, so this approach works où ping scans, broadcast pings et port scans ne (due to firewalls, OS policy, etc.).
