Gelatinous Slime is an item similar to the Slimeball items, except it is dropped by Blue Slimes when killed. Unlike Slimeballs, Gelatinous Slime can actually be eaten, which restores 2 points of hunger. Just like Slimeballs, Gelatinous Slime can be used to craft Sticky Pistons, Slime Brick, Slimy Mud, and Magma Cream. Gelatinous Slime can also be crafted with anything that would normally use Slimeballs in it's recipe.
Gelatinous Slime Drop
If you put a Gelatinous Slime onto a Drying Rack and wait 5 minutes, it will turn into a Gelatinous Slime Drop. The Gelatinous Slime Drop is a food item that restores 3 hunger when consumed.
Blue Slime Crystal
Gelatinous Slime, just like Green Slime, cannot be worked directly in a Part Builder. Instead, put into a Crafting Table 4 Gelatinous Slime, 1 Dirt, and 1 Sand to make 1 Slimy Mud. Then, cook the Slimy Mud in a Furnace to make a Slime Crystal. It is these slime crystals that are then used in the Part Builder.
Note that tool material costs are in terms of the Slime Crystals and that 4 units of the raw slime are required to make 1 crystal. So, to make a Crossbow Limb (Material Cost of 4) out of blue slime requires obtaining 16 Gelatinous Slime.
Congealed Blue Slime
Congealed Blue Slime is a block made from four Gelatinous Slime. It can also be found on floating Slime Islands around the "lake." It can be crafted back into 4 balls of Gelatinous Slime, again.
Slime Channels are used to make bounce pads. They can be used as a placeable water stream, and can be used in the Nether. This allows for Overworld-based mob farms that use water to work there.
Due to the early availability of Gelatinous Slime on Slime Islands and the resourcefulness of the Gelatinous Slime itself, one may climb the islands and gather Slime to use as an alternative food source, or as a resource for forging tools (via Slime Crystal)