tcpdump prints a description of the contents of packets on a network interface which match a given boolean expression. It can also be run with the -w flag, which causes it to save the packet data to a file for later analysis, and/or with the -r flag, which causes it to read from a saved packet file rather than to read packets from a network interface. In all cases, only packets which match the expression will be processed by tcpdump. tcpdump logs more than just TCP, IP, or ethernet packets, but has a whole suite of decoders, including ones for USB.
tcpick is a textmode sniffer that can track TCP streams and saves the data captured in files or displays them in the terminal. It is useful for picking files in a passive way. It can store all connections in different files, or it can display all the stream on the terminal (using colors too).
Tdbengine is an RDBMS with an integrated programming language. It represents the enhancement of the famous DOS-TDB, and is designed to handle databases on the Web. It connects to the Web server using the standard CGI interface, or runs on the command line. It is very small (about 400 KBytes), extremely quick, and easy to administrate. Its features are full text indexing, an automatic data link system, and the script language EASY, which replaces the commonly used SQL with its modular code.