NetworkActiv Port Scanner
NetworkActiv Port Scanner is a network exploration and administration tool that allows you to scan and explore internal LANs and external WANs. Because of the versatility and choosable operating modes available in NetworkActiv Port Scanner, it may be used by experienced network administrators as... NetworkActiv Port Scanner provides scanning performance simply not found in other Windows based network scanners, but one will need to actually try it to understand just how fast a network scan can be.
http://www.networkactiv.com/NetworkActivPortScannerV4.0.exe - 2Mb - Download - Screenshot

Vypress Chat
Vypress Chat is a user-friendly application for real-time chatting in small or home office (SOHO) local networks. This unique chat software features an easy-to-understand format for text-based conferences and discussions. Vypress Chat does not require an Internet connection or a dedicated server... You get an interface comparable to mIRC's graphical IRC interface, and system tray functionality similar to that of ICQ. ... Also available is IP Multicast protocol support. ... The IP Multicast allows Vypress Chat to operate over WANs or in complex routed network environment.
http://www.vypress.com/ftp/VyChat21.msi - 2Mb - Download - Screenshot