hslogger is a logging framework for Haskell, roughly similar to Python's logging module. hpodder lets each log message have a priority and source be associated with it. The programmer can then define global handlers that route or filter messages based on the priority and source. hslogger also has a syslog handler built in.
timeplotters is a collection of command line tools for visualizing temporal data. It is especially useful for visualizing data from ad-hoc program logs, helping you to spot patterns and anomalies that you would not otherwise see by just watching how the program works or by looking at the logs with the naked eye. Its input format is tailored to event types typically seen in program logs, and the visualization methods are tailored to the questions typically asked about program performance (e.g. distribution of activity durations).