IceScan is a free open source network analyzing and security auditing tool for Unix-like and Windows operating systems. It uses libpcap, a packet capture and filtering library.
aircrack-ng is a set of tools for auditing wireless networks. It's an enhanced/reborn version of aircrack. It consists of airodump, aireplay, aircrack, airdecap, and some tools to handle capture files (merge, convert, etc.).