What is Karmasphere?
Karmasphere is an open reputation system with limitless application, intended to supercede simple DNSBLs. It permits multiple identities per query, with native transport of IP4, IP6, domain, URL, numeric, symbolic and other identity formats. Client libraries exist for all the major MTA's and API's for most applicable programming languages.
Do you have a project which needs reputation?
Do you have a blog which gets spam comments? Do you have an inbox which gets spam mail? Do you carry out transactions with unknown users? Karmasphere will let you publish and query information about URLs, domains, email addresses, IPs, or anything else, so you can decide which messages to accept and which to reject.
If there isn't already a plugin for your system, start with a client library and write one. Join the mailing list for more help.