Slayers d20 was of course Guardians of Order's attempt at making a D&D-esque ruleset starring Lina Inverse and general fantasy mayhem.
I can't rewrite Slayers d20 with IP, but per the OGL I do have access to the mechanics, so that's what I've worked with, turning it into a system I call Insane Fantasy.
You can access the alpha draft of the rules here:
Yes, that is a link to a Paizo forum post, which in turn links to the items on GoogleDocs. Apologies for linking to a link that links to links, but I'd rather direct everyone to the same place. Comments are enabled on the documents themselves so you do not need to comment on the message board--and of course you could comment here as well.
If I am ever happy with Insane Fantasy that I'd want them to be totally public, I'd probably post them to some kind of game wiki for free here. This project is entirely for fun and not profit--although I'd still like it to be GOOD, so feedback is much appreciated.