I operate an RBL/ORDB-style DNS lookup service for blocking people who have sent me spam. Access is in the normal fashion; to look up A.B.C.D send a DNS "A" request for D.C.B.A.spam.pedantic.org. and you will get a result of 127.0.0.2 if and only if that address is in the listing.
To request removal from the spam list, email webmaster@pedantic.org with a description of what was done to solve the problem that allowed that address to send spam. Please note that if you are using a shared email server from an email service provider like Google, you'll need to have them deal with the issue and contact us.
I have information about the yellow dots placed on pages by some models of color printers. This is part of the EFF effort to track down and decipher such dots.