nmap

List IPs on a Network

$ nmap -sP 192.168.1.0/24

Or, you can do a range:

$ nmap -sP 192.168.1.0-10

Scan for Ports on a Network

$ nmap -sF -p22 192.168.41.0/24

Further Reading

https://github.com/bwaldvogel/neighbourhood

http://community.spiceworks.com/how_to/show/583

http://taufanlubis.wordpress.com/2007/10/20/ip-and-port-scanning-using-nmap-network-mapper-in-ubuntu/

http://www.itauthor.com/2011/08/28/scan-for-available-ip-addresses/

http://nmap.org/nmap_doc.html

http://www.petri.co.il/port-scanning-with-nmap.htm