Gspoof is a GTK+ program written in the C language which makes it easier and more accurate to build and send TCP packets with or without a data-payload. It's possible to modify TCP/IP fields and also ethernet header working to Link Level. You can send one or more packets together. It runs also in "console mode" without X and so you can compile it without GTK+.
Nast is a packet sniffer and a LAN analyzer based on Libnet and Libpcap. It can sniff the packets on a network interface in normal mode or in promiscuous mode. It dumps the headers of packets and the payload in ASCII or ASCII-hex format. Various packet filters can be applied. The data sniffed can be saved in a separate file. As an analysis tool, it can check for other NICs on the network which are set in promiscuous mode, build a list of all hosts on a LAN, find a gateway, perform port scanning on a multiple hosts, catch daemon banners, follow the TCP data stream, reset a connection, and determine whether a link type is a hub or switch.
Visual Interactive Datapipe (Vida) is an interactive visual datapipe for all *nix systems, which allows socket communications to be redirected over pipes. It features an ncurses interface that allows the creation of multiple datapipes, each supporting multiple connections. It is possible to sniff and log traffic in various ways, hijack piped connections, perform DNS hijacking on switched LANs, and much more.