http://www.incursion-roguelike.org
I figure there's got to be a few Roguelike fans around these boards, and I also figure that unless you hang out on the miscellaneous Roguelike group on Usenet, (or Quarter to Three), there's a pretty fair chance you haven't heard of this one. I certainly hadn't until very recently. Let me just say, it's still in the middle of development, but it's very playable even now and it is AWESOME.
It's based, as the topic description suggests, on OGL. Which means you can look forward to a character that's not just a race/class combo like many Roguelikes (though those are there, and both have profound impacts on your character's nature), but also feats and skills, the latter of which have a wide variety of uses. Almost all of the skills have two or three distinct functions, sometimes as many as eight or nine. Also, prestige classes, multiclassing on a level by level basis, clerical domains...all in right now.
Of course, they've been modified a bit both for balance and for the particular needs of the game. Races have probably seen the most change, followed shortly by skills - it's not so much that the skills vary widely from what they do in D&D, but the skill system has been significantly modified. You can't advance non-class skills at *all* (fortunately, races also give you "
class"
skills, and there's a feat that can be taken repeatedly that will make a given skill function as a class skill.), and there are some uses/benefits of skills that only function if they're a class skill. Likewise, you don't get as many points to spend on skills.
Anyway, there's been a bunch of other changes, but the important thing is the wide range of interactions possible. Racial special abilities, class special abilities, combat maneuvers, magic, skills, terrain types, monster templates, all taken into account. There are tunnels that are awkward to move through if you're of medium size, and impossible to pass through if large. There are ice rooms, which require balance checks to keep your footing in combat. Climb will (at advanced levels) allow you to climb across the ceiling, with the right gear. You can bluff neutral monsters into taking your side, or simply send them haring off across the dungeon. Creatures actually use equipment and will, if intelligent, pick up and use treasure as well. Any monster can be generated as a standard member of that type or pick up class levels or special templates which you may not be able to identify without the proper knowledge...at least until their special features become apparent. Like when the spellstitched skeletal foot soldier summons a flaming sphere.
I could go on at length. My main quibbles are the inventory system, which is a bit awkward at first (and I'd like to be able to look at items in my backpack, but oh well.), and the rest system. The latter is a deliberate design decision to force players to make more tactical decisions about even relatively renewable resources. I can sort of see where the guy's coming from, but it's something I've never liked very much and in its current form it also seems unbalanced in the direction of spontaneously killing you.