nmap - scan an ip range for a single open port

nmap -p80 192.168.0.0/24 -oG - | grep 80/open

Example

[modinfo@arch-pc ~]$ nmap -p80 192.168.0.0/24 -oG - | grep 80/open
Host: 192.168.0.1 (router)    Ports: 80/open/tcp//http///
Host: 192.168.0.100 (aaa)    Ports: 80/open/tcp//http///
Host: 192.168.0.126 (nsa310)    Ports: 80/open/tcp//http///
Host: 192.168.0.133 (arch-pc)    Ports: 80/open/tcp//http///