Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.
Dreamboard - DreamBoard lets you take control over the homescreen of your jailbroken iPhone.
tcpdump - tcpdump is a common packet analyzer that runs under the command line.
Lockinfo - You can find this app in Cydia - Tweaks.
SmartSniff - SmartSniff is a packet sniffer that capture TCP/IP packets and display them as sequence of conversations between clients and servers.
Cylinder - Sexy homescreen icon animations