I came across this raytracer written in Haskell in one day about 7 years ago.
Here's a quote from the source code:
-- I wrote this in a day to learn Haskell. I was pretty impressed by -- the speed of development. Compared to C/C++/Java, you spend much -- more time thinking about the problem rather than the implementation -- language. You don't need to worry about memory management. Your -- code isn't littered with detail about *how* to do things (ie. in -- Haskell you'd use map in places where you'd have a for loop in C, -- and you don't have to explicitly state the loop variable or the -- number of iterations). The strict typechecking and the interpreted -- nature of hugs means that most errors are flagged quickly. It -- doesn't stop you making logic errors though, but it's quite easy to -- test functions individual to work out what's going wrong (big win -- for interpreters). It's pretty concise too (around 160 lines of -- actual code). And the performance isn't all that bad.