DNSBL.im
Involvement
I help manage DNSBL.im, a DNSBL (Domain Name Service BlackList).
Myself and Robert Whitney have been working on it for over a year, it currently boasts an API and a few other tools used to help manage it.
API
I’ve been the one constructing the API, its a public DNSBL but there is restricted access to the API. It has multiple abilities, involving adding, removing and checking.