Available is a simple whois Applet that will probe any server on the Internet to tell you if it is available/up/running. As a side effect, it will tell you the IP address given the host name, or the host name given the IP address.
Colasoft MAC Scanner is a scan tool for scanning IP address and MAC address. It can detect the specified subnets and scan the MAC addresses and IP addresses.
VisualRoute combines several essential network tools to analyze Internet connections and identify bottlenecks that cause slow response. The path of each connection is shown on a world map, domain and network Whois lookups enable quick reporting.
Anti-Spam Blacklist Thing lets you check to see if a given IP address or hostname is on one of up to 20 different anti-spam blacklists. Anti-Spam Blacklist Thing is provided by SpamButcher completely free of charge.