NetworkMiner is a Network Forensic Analysis Tool for Windows. NetworkMiner can be used as a passive network sniffer/packet capturing tool in order to detect operating systems, sessions, hostnames, open ports etc. without putting any traffic on the network. NetworkMiner can also parse pcap files for off-line analysis and to regenerate/reassemble transmitted files and certificates from pcap files. In contrast to other sniffers like Wireshark, NetworkMiner's display focuses on hosts and their attributes rather than raw packets.
For downloads and more information,
visit the NetworkMiner homepage.
I'm testing the free version and although it doesn't provide executive reports, it does allow having general overview of the top talkers in the network and the connections made by each. Easy to use and read for non-experts. It also has some nice features like content extraction and DNS queries analysis.