Cool! Benjamin Pollack posted a brillant piece describing the value of the REPL, the "Read-Eval-Print-Loop" that makes environments like Smalltalk, Python and Ruby so absolutely superior to the typical "Code-Compile-Test-Debug" cycle of other tools. Good read.
Oh! And I found it via a nice bit that says Dynamic languages work closer to how you design software. Also a nice read with some solid backing for an assumption I've long held.