So, why review free RPGs?
I've two motives for posting reviews of free RPGs. One, is simply to increase traffic to Mythopoetic Games. Reviews tend to attract people in a way that downloads may not. The second is more altruistic. There are a lot of good free games out there and very few of them get the press they deserve. Of course I'll happily acknowledge that about 90% of what is out there is not worth the bandwidth it takes to view. So too often it is easy to look through three or four games and despair of finding anything worthwhile. Hence I do some of the serious legwork so that you can read a few reviews of good, worthwhile free games.

And for that matter what are your guidelines for a review?
I am mostly interested in reviewing games that I think will appeal to a wide audience. There are some really excellent one-shot, rules lite games out there, but these simply don't appeal to the majority of gamers (in my subjective opinion).

So what I am looking for are primarily rules-medium, mostly or wholly complete games that either present a solidly detailed setting or take the generic fantasy, anime, science fiction, supers or horror route. I am okay with a game stating something like, 'this is a fantasy game system, but you need to create your own setting', but will give preference to the more setting-intense games that are out there.
 
Some other good free RPG resources...
There are several good lists of free RPGs available on the web. John Kim's page is excellent as is Chris's Compendium of free RPGs. The Great RGP Archive is worth a look in too as is the Roleplaying Directory's list of free RPGs. Google has a surprisingly good directory of free games organised by page-count and divided up by genre. And of course we can always rely on RPG.net to give us a little something too.

If you'd like to read some more then the reviews at The Forge (some of which are for free games) and the list of indie game sites.