Note: This is an incomplete list, a large number of people have contributed to the project.
Freenet is based on Ian's paper "A Distributed Decentralised Information Storage and Retrieval System". Ian started the Freenet Project around July of 1999, and continues to coordinate the project. In his day job, Ian is the founder and CEO of SenseArray.
Matthew has been working on Freenet since before the 0.5 release. His work and that of others has resulted in dramatic improvements to the performance and stability of the network.
Oskar was also one of the earliest contributors to the Freenet project, and has made some important theoretical breakthroughs that lead to the beginning of Freenet 0.7, see the papers page.
Since 2003, Florent has improved various aspects of the software and performed the project's system administration. In his day job, he is the Technical Director of Matta Consulting, a boutique security consultancy firm.
Scott is responsible for the implementation of much of the cryptography elements within Freenet.
Steven helps with administration of Freenet Project Inc, and is an advisor to the project on business and publicity matters.
Michael has mostly contributed detailed simulations as part of the Google Summer of Code. He has been helpful in designing the new transport layer.
Dave's main contribution has been Freemail, his Summer of Code project to build a working email-over-freenet system, as well as some debugging and core work in various places.
Robert has helped improve the speed and security of Freenet by finding two major bugs, and has recently contributed some code.
David (Zothar) has helped the Freenet project as time permits and interest directs, including configuration, statistics and peer management via FCP, the FProxy stats page and Node 2 Node Messages (N2NM/N2NTMs).
And hundreds of others, who either haven't asked to be added here, who prefer to remain nameless, or who we just haven't got around to thanking. Not to mention thousands of users, testers, and donors!