libKISSlog is a trivial lightweight C++ template library designed and written according to the KISS (Keep It Simple and Straightforward) principle. It leans heavily on STL for keeping its implementation as simple as its usage, and tries to provide C++ developers with a lightweight, paradigm-pure, and flexible alternative to logging libraries which use design and/or implementation decisions which at least the author of libKISSlog believes to be questionable. Its easiest to explain why libKISSlog would be suitable for your needs by listing the things which libKISSlog does not choose to use or do: no singletons or other forms of mutable global state, no macros, no attempt to fit the Java runtime everything model onto a C++ library, no attempt to be a Java-style (bloated) framework, no attempt to make the choice for you of whether you need thread safety, and no compromise on simplicity in order to facilitate questionable inner-loop logging practices.
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.
The Logfile Navigator, lnav for short, is a curses-based tool for viewing and analyzing log files. The value added by lnav over text viewers or editors is that it takes advantage of any semantic information that can be gleaned from the log file, such as timestamps and log levels. Using this extra semantic information, lnav can do things like interleaving messages from different files, generate histograms of messages over time, and provide hotkeys for navigating through the file. These features are meant to allow the user to quickly and efficiently focus on problems.
Trafficmeter is a traffic collecting and logging system. It collects and groups packets by time, source IP, destination IP, protocol, source port, and destination port. You can get a detailed log of traffic for every IP without any daemon configuration work. It also gives statistics of IP incoming and outgoing traffic for a time period.
Multiplexing Console Manager is a daemon that provides multiplexed access to network accessible consoles (e.g. terminal servers, Serial Over LAN, etc). Features include kerberized authentication, ACL based entitlements, multiple viewers/editors, full logging (simple text and timestamped, replayable XML) of all output.
Zibu is a small tool that allows you to cyclically compare access permissions and checksums of files provided by users, with a database generated at first run (to be exact, generated with --init or --update mode). But its main feature is restoring valid access permissions, and/or executing your commands when checksums are invalid.