gauger is a lightweight performance recording and monitoring tool, aimed at detecting regressions (or sudden impovements) in any measurable metric. It is mainly intended for software development, but can be used for other purposes such as network monitoring or meteorological logging. It collects measurments made by a number of clients (potentially behind firewalls) on a central server and allows you to visualize and analyze the data later. It offers a central log server, Python, Java, and C interfaces for the clients, and a Web interface to browse the data. It allows you to view graphs of the data per host or per metric, selecting the desired ranges and sizes, and allows you to download the data in a gnuplot script for further processing.
FlatTraffic is a Web interface for analysing netflow records and showing statistics designed to make it clear and easy to determine which hosts on a network are consuming data. It has been primarily designed for use by networking and servers geeks who have to endure the pain of data-capped Internet Service Providers, something that's unfortunately rather common in the Australia/New Zealand region in particular.