Fans of OD&D (even the recent reprint) and Swords & Wizardry who are looking for some new options to add into play may want to consider Jimm Johnson’s house rules Planet Eris: Booklet 1 – House Rules. Apart from adding in options for demi-humans (non-humans), it tweaks some of the existing classes, and adds in a lot of other options that can be found in some of the more advanced versions of the games all without quite losing the OD&D flavor.
The booklet can be downloaded from Jimm’s blog The Contemptible Cube of Quazar.
I mean, look at that cover. Doesn’t that just scream OD&D to you?