Because of the GSL requirements that publishers produce a given line only for 4e several companies, starting with Mongoose Publishing, started putting a lot of their 3.x/OGL material into what they call . I own a goodly chunk of the books that they are putting up, and can say that I am glad that they will not simply be allowed to disappear.
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In particular the Quintessential Series by Mongoose. I have gotten a lot of use out of the side systems that they tucked into each of the books - from Libraries in Quintessential Wizards to the Open Mass Combat System in Quintessential Fighter (this last is still awaiting entry, since it will have to be done manually). The Library rules would have made Quintessential Wizard a worthwhile purchase for me, all by its lonesome, but there was other good stuff tucked away as well.
Ironically, The Quintessential Wizard was written by Mike Mearls....
Paizo has started releasing some of the Pathfinder OGL information on the Wiki, which I think is a nice touch, since Pathfinder is not one of the game lines being killed due to 4e.
If you want to take a look at some of the ways they have tweaked some of the classic D&D monsters then you may want to go there and take a gander.
Recently they also started putting up 4e material, but for me the 3.x stuff is where my interests lie.
The Auld Grump
