Wireshark is an open source network sniffing utility to analyze network traffic.

Wappalyzer is a cross-platform utility that uncovers the technologies used on websites.

Hiren's BootCD (HBCD) is a bootable CD containing a number of diagnostic programs such as partitioning agents, system performance

Charles is an HTTP proxy / HTTP monitor / Reverse Proxy that enables a developer to view all of the HTTP and SSL / HTTPS traffic.