An IPFIX implementation for Ruby, which transcodes Ruby hashes into records in IPFIX Messages. The official release is available from github.
An IPFIX implementation written in C++, also available at github. (Designed and implemented with Stephan Neuhaus at ETH)
Stuff hosted elsewhere
YAF (Yet Another Flowmeter) is a high-performance, software-based IPFIX flow metering and exporting process. (initial lead developer and principal maintainer to May 2008)
libfixbuf is a high-performance IPFIX implementation library in C. (initial lead developer and principal maintainer to May 2008)