Are there any cards that turn creatures into land?
There are four cards that explicitly turn creatures into lands.

Life and Limb makes all Saprolings Forests.
Song of the Dryads turns any single permanent into a Forest
Imprisoned in the Moon turns any creature, land, or planeswalker into a land with no subtype that can only tap for {C}.
Ashaya, Soul of the Wild turns all creatures you control into forests.

In addition, there are 4 cards that can make arbitrary creatures copies of specific creature permanents: Cytoshape, Infinite Reflection, Echoing Equation, and Mirrorweave. If you make a land into a creature (with a card with Awaken, for example), and then cast one of those spells targeting that land, the other creature(s) will become copies of the land.
Finally, any creature that enters the battlefield as a copy of a creature permanent (i.e. Clone) or can become a copy of a creature permanent (i.e. Shapesharer), can become a copy of an animated land, which will result in it being just a land.