First of all, congrats on the site its has lots of great information for beginners, an more advanced users.
Now a couple of things that I have been wondering, and maybe with all your expertise can probably do, is some tutorials about:
-Generating a 3D terrain from a height map (simple way of loading a map)
-Generate a height map using perlin noise (making more dinamic maps)
-Using the perlin noise to generate the next seccion of the map (so if in the previews tutorial you loaded cuadrant 0,0 to 32,32, for example, now I want to load the next section in any direction for example, 32,0 to 64,32)
-Change perlin noise into a 3d perlin noise to generate overhangs
-Making caves in 3d space, that look nice, maybe you can use another type of noise for this.
-Transforming the map into other types of vertices, for example, each vertice is a triangle (the look of sim city 2000), each vertice is a cube(the look of infiniminer/minecraft), and so on.
-making the vertices that are behind your camera FOV dissapear (not get loaded at all)
-making the vertices that are behind other objects dissaper (not get loaded at all)
-make a camera for FPS kind of look
-make a camera for 3rd person view
-smooth transition from FPS camera to 3rd Person, and back.
-making a model within XNA, and not use a .x or .fbx premade model, for example a guy made of spheres and tubes, kind of bomberman looking.
-animating that character, simple walk, run
-adding gravity, make your character jump.
-making 3d sprites within XNA, for example made of spheres or cubes. Like a fire ball, or a sword/shield.
-adding 3d effects to characters of objects, such as a power up/level up.
-shooting stuff in 3d space, for example have you character shoot a 3d fireball, and make it hit stuff, like targets or ground.
-placing random stuff in your map, to make it look good, for example a tree. (not a tree sprite, a 3d tree model make within xna, maybe with a blob of leafs made of spheres with procedural generation to make the trees different from each other)
-placing enemies in your map, maybe copies of you, or a character with a different colored face.
-make enemies follow you
-make enemies attack you
-make enemies and you wield a sword.
-make everyone hit with the sword.
-How to make an inventory screen, pick up items from the floor, store them in your inventory.
-——yeah i have many many ideas for tutorials I know.
I'm quite old right now and I have played, TONS of games, and I have around 10 years of programming experience, but I've never tried making a game, I now have 2 weeks into XNA, and I've made quite some tutorials for lots of fun stuff, but that probably raised more questions than answers so far. These tutorial ideas are just some of those questions I have, and as a beginner in game programming probably lots of other people have the same questions as I do.
I have already make a quick pass to look over the tutorials you have in your site, and I will make them all to see if I can find some answers to my questions.
Cheers on the great site, and hopefully you can greatly expand it.