Good point. I just found my first project. It needs bricks and blocks, but I have no idea how to make or buy them. (I'm assuming it has something to do with the machines.)
An item I got seems to be missing from the list of items. I don't want to ruin part of the game for people so I'll just say I got my hands on some sort of "kindness" item from a certain character related to one of the giants, lol. I wish I remembered what it was called, and I don't even know how the item works, which is why I was looking through the items page, in the first place.
Spigot, turnip and radishes have been on there since at least sometime late into the alpha (I came in around December and they were there... I believe.)
We've been waiting for gum trees for awhile now. I suspect "gum" may be used in construction.
preciousssss is missing, how in the world could you forget precioussss, just sayin' ;p
Gum trees were removed, I don't know why. Can think of all sorts of fun things to do with sticky stuff ...
Also the characters are missing, though possibly a different page would be more appropriate for them as they aren't exactly items, Yoga Froggy and The Rube.
Uncle Friendly, The Meal Vendor, Gwedolyn and her bag and wood friends, and Helga could understandably be listed in locations or vendors somewhere ....
Speaking of trees, they are all missing except in bean form. It would be very helpful to have something which shows the various life cycles of the trees.
And Dirt patches and Garden plots, they aren't there either , hey this is kinda fun ...
quoins are missing and ... teleportation tokens and what do the subway tickets look like ?
People - if you're talking about the Encylopedia, not the Wiki, then yeah, it's missing everything in the game that's not an item, a skill, or a badge. That includes animals (with the exception of the juvenile forms and hog-tied piggies), plants (with the exception of seeds and beans), and "people", among other things.
But the wiki is another story entirely. It's missing all sorts of stuff, but we can expand it ourselves! Maybe collectively, we could get all of this stuff documented - and better than the Encyclopedia.
ETA: Anyone who wants to write for the wiki could start here, with unwritten pages. As of now, there's no article for the Blockmaker, or Gwendolyn.