DNSSEC
I wrote one of the first DNSSEC signers that was capable of using a HSM to store the cryptographic keys. That code now forms part of LDNS. This work lead to the realization that a way to store key and signing policy was needed and the invention of the concept of a KASP database.
These days I continue this work by contributing to OpenDNSSEC.
NSCP
I wrote a proof of concept implementaton of NSCP for Nominet.
Visualization
Recently, I started thinking about visualizations after seeing Roy’s 3DHeatmaps and have been looking at Many Eyes for ideas.