Python quite famously uses indentation to syntactically define blocks of code. (See Compound statements in the Python Language Reference). After years of using Python I'm still intrigued by and very fond of this syntax feature.
But I wonder: Apart from Python and its "predecessor"(*) language ABC which other programming languages are out there using indentation for definition of code blocks? Code blocks means here "multiple statements which in some way are treated as one component".
I'm particularly interested in practical programming languages, but esoteric languages might be worth mentioning as well.
(*): "Predecessor" is my choice of word in default of knowing here a better one. Guido van Rossum, the creator of Python, described the relationship between Python and ABC regarding indentation in an interview like this: "The choice of indentation for grouping was not a novel concept in Python; I inherited this from ABC."