RadiusSplit is a Perl program designed to take, as input, one or more large RADIUS accounting "detail" log files, and split them out into individual files - one per user. The net result is that you will have a detail file per user, which can be passed to other RADIUS parsing logfile analysers (e.g. RadiusReport) so they run much faster (usually be a factor of several hundred), since they don't have to parse and discard the non-relevant data.
Web Log Trends Analyzer provides a work-around for a "bug" in some popular commercial Log Analyzer products, which makes them unable to process multiple log files for overlapping periods of time. If you like your commercial Log Analyzer, and don't feel like upgrading just yet, this little Perl script will do the trick nicely. Simply specify a list of all your log files, and it will consolidate them into a single log file, sorted by time. The output log will work with your commercial Log Analyzer product without a hitch, allowing you to continue using it to generate reports.
MRTG-eth-probe provides a probe for the Multi Router Traffic Grapher, generating statistics for network devices that do not support the SNMP protocol. It reads interface stats from /proc/net/dev (or some other file you configure), and generates an output suitable for MRTG by parsing the file. Reading of remote data via SSH is supported.
flow-tools is a set of programs for processing and managing NetFlow exports from Cisco and Juniper routers. The tools included are: flow-capture, flow-cat, flow-dscan, flow-expire, flow-export, flow-fanout, flow-filter, flow-gen, flow-header, flow-import, flow-mask, flow-merge, flow-nfilter, flow-print, flow-receive, flow-report, flow-send, flow-split, flow-stat, flow-tag, and flow-xlate.