aircrack-ng is a set of tools for auditing wireless networks. It's an enhanced/reborn version of aircrack. It consists of airodump (an 802.11 packet capture program), aireplay (an 802.11 packet injection program), aircrack (static WEP and WPA-PSK cracking), airdecap (decrypts WEP/WPA capture files), and some tools to handle capture files (merge, convert, etc.).
Alarm Pinger (apinger) is a little tool which monitors various IP devices by simple ICMP echo requests. Unlike most Perl or shell script tools, it does not spawn processes or use much CPU time, and is ideal for when one wants continuous monitoring and fast response upon target failure. It is written in C and supports both IPv4 and IPv6.
Andrisoft WANSIGHT is a fully featured network traffic analyzer and collector. It provides in-depth traffic analysis, traffic accounting, and bandwidth monitoring, and enables you to generate complex traffic reports, graphs, and tops, instantly pin down the cause of network incidents, understand patterns in application performance, and make the right capacity planning decisions. It supports 10GbE packet sniffing and NetFlow, sFlow, and IPFIX.
BGPHist is a tool that receives MP-BGP updates, decodes them, and writes them to a database for logging and monitoring purposes. It supports not only Internet routes, but also IPv4 VPN, IPV6 VPN, and L2VPN. It sounds text output, MySQL databases, and Oracle databases. For the MySQL backend, there is also a simple PHP frontend. It could be used to monitor and log an ISP's customer activity for Internet and VPNs, as a passive BGP looking glass, or as a backend for some external monitoring and accounting system.