Angry IP Scanner - Open-source and cross-platform network scanner designed to be fast and simple to use
WakeMeOnLan - Turn on computers on your local area network by sending Wake-on-LAN packets.
Fing - Discover which devices are connected to any Wi-Fi network, map devices, detect intruders, assess...
Advanced Port Scanner - Advanced Port Scanner is a fast and free software for port scanning.
Wireless Network Watcher - scans your wireless network and displays the list of all computers and devices that are currently connected to your network.
gWakeOnLan - gWakeOnLan is a GTK+ utility to awake turned off computers through the Wake on LAN feature.