So in my adventures, I have found:
Slime Ball - A placeable ball that has no use as of yet.
Water Lilies - Previously only obtainable in the Easter pack, these are placeable.
Green Goop - This was craftable, and is now able to be mined.
Slime Splat - Not sure how this was obtained before, but it was around. This is placeable.
Water is also found in these mines.
The giant mushrooms (can't remember name) are a 3x3, and similar to doors, cannot be placed beside each other exactly, but I wove them anyways. The can be placed in a grid.
The tree tops can be passed through (like rainbow blocks)
If you did not already notice, the deep forest mines are 100x100, rather than the smaller size.