TCP Profiles Manager

TCP Profiles Manager is a utility to easily change local IP address, subnet mask, network, gateway, DNS ... all without rebooting.
BuduIP

BuduIP will automatically ping IP range specified by the user to reveal any taken or vacant IP address.
Network Scanner

Network Scanner is a free multi-threaded Port, IP, NetBIOS and SNMP scanner with many advanced features.
IPaddress

IPaddress is a tiny utility that you can use to determine your IP address and lets you copy it to the computer's Clipboard.
IP-MAC Scanner

Powerful tool for network management and network analysis
Free Port Explorer

The Free Port Explorer shows the ports that are currently open on your computer
IP Pig Port Scanner

The IP Pig port scanner scans your computer for all open and closed ports and tells you what protocol \ service is using that port.
LanFriends

Scan your network and discover your IP neighbors.
MaxPortScanner

a simple port scanner to scan all ports ( 0 - 65536), In local or remote hosts.