Analog PHP is a short and simple logging package for PHP 5.3+ based around the idea of using closures for configurability and extensibility. It functions as a static class, but you can completely control the handling of log messages through closures (aka anonymous functions), and it also comes with a dozen pre-written handlers. It is well-documented, with examples for each type of log handler, and ultra-concise. The core is literally only 43 lines of clear, non-obfuscated code, and the whole is only a fraction of the size of comparable packages (for example, 293 total lines vs 1021 for Monolog).
Service Guardian aims to protect servers against various things such as resource exhaustion and connection floods. It can measure the number of connections to servers' ports and, after a grace time period, compares and sees if the host is still in violation of the specified settings. If a host is in violation of the settings, it will be filtered out and dropped via netfilter/iptables.
pdr (personal data recorder) and pdx (personal data expert) are applications that collect and evaluate mostly numeric personal data. The intended use case is for logging individual medical data (blood sugar, blood pressure, body temperature, weight, heart rate, and medications), but they can also be used for technical, sports, fitness, weather, environmental, or financial data. They work on a continuous flow of numbers in time that you want to monitor. Every data item can also be commented by text. pdr can use Twitter and email accounts for data input, which makes mobile phones usable for data input. It is one of the few free applications for diabetics.
Vee is a command-line blog tool that is very portable across Unix systems. It provides an interactive as well as a batch interface to maintain a log of entries. Formatting is done using a module architecture that allows a high degree of customization. There are minimal flags and no set up is required.
Picviz is a parallel coordinates plotter which enables easy scripting from various types of input (such as tcpdump, syslog, iptables logs, or Apache logs) to visualize your data and discover interesting results quickly. Its primary goal is to graph data in order to be able to quickly analyze problems and find correlations among variables. With security analysis in mind, the program has been designed to be very flexible, able to graph millions of events.
Callstats collects and displays call statistics for Siemens HiPath OpenOffice ME in a pretty Web interface. It may work with other Siemens HiPath devices (probably Hipath 3000). With some modifications, it could be adapted to your own system. It has 3 parts: -tcp->text log (via netlog); text log->sqlite database (PHP script); and a Web interface to the SQLite database (PHP). It has been tested without problems in a 50-user installation fulltime since 2009.
Ipt_fw is a firewall for Linux based on iptables. It is designed for client systems. Ipt_fw outputs a shell script containing iptables commands, so inspection of the settings it creates is easy. The configuration files are made in LibreOffice（OpenOffice）Calc. Making of the firewall and a machine using the firewall are separated. It allows you to set the user level and features detailed logging, IP address blacklist management, and iptables integrity.
jmxtrans is effectively the missing connector between JMX and whatever logging or graphing package that you can dream up. jmxtrans is very powerful tool that reads JSON configuration files specifying servers/ports and JMX domains/attributes and then outputs the data in whatever format you want via special "Writer" objects that you can code up yourself. It does this with a very efficient engine design that will scale to querying literally thousands of machines. The core engine is pretty solid and writers are included for cacti/rrdtool, graphite, and stdout.