ArgoUML is a pure Java open source UML CASE tool that provides cognitive support for object-oriented design. ArgoUML provides some of the same editing and code generation features of a commercial CASE tool, but it focuses on features that enhance usability and support the cognitive needs of designers. Uses XML file formats: XMI and PGML.
This is a handy little library which provides a packet filtering mechanism based on the BSD packet filter (BPF). Most notably, tcpdump needs this to work, and there is also a perl module (still in beta) which can use this as well. In plain english, if you want to write your own network traffic analyzer, this is the place to start.
bzip2 is a portable, lossless data compressor based on the Burrows-Wheeler transform. It achieves good compression and runs on practically every (32/64-bit) platform in the known universe. The compression engine is also available as a library (libbz2), should you desire a programmatic interface.
Flex is a tool for generating programs that recognize lexical patterns in text. There are many applications for Flex, including writing compilers in conjunction with GNU Bison. Flex is a free implementation of the well known Lex program. It features a Lex compatibility mode, and also provides several new features such as exclusive start conditions.
The NET-SNMP (formerly UCD-SNMP) package contains various tools relating to the Simple Network Management Protocol including an extensible agent, an SNMP library, tools to request or set information from SNMP agents, tools to generate and handle SNMP traps, a version of the unix 'netstat' command using SNMP and a Tk/perl mib browser. It was originally based on the Carnegie Mellon University SNMP implementation (version 126.96.36.199), but has been greatly enhanced, ported and fixed and barely resembles the original package anymore.