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 email@example.com.
Important: As of 2015-01-02, the netblock.pedantic.org no longer exists. If you find yourself getting ICMP rejections in response to queries, it is because you are still using this list. Contact the address above after fixing the problem to have the ICMP restriction lifted.
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.