I've recently been learning Haskell. As part of that, I'm implementing Huffman Coding. This is my first real project in the language. It's been overall quite pleasant, and has taught me a lot.

The biggest lesson has been thoroughly meta: compression tasks are a great way to learn a language/environment. For this project, I had to learn how to use modules, do I/O, mangle arrays, and define tree structures. It might not look like too much, but that's actually a huge amount of stuff to shove into a couple weekends of hacking.

Other things I've learned (or relearned), in no particular order:

• You'll get a reasonable answer if you hop on IRC to for help in #haskell.
• "You remember the mental leap from imperative languages to OCaml? I had about the same level of change going from OCaml to Haskell." -- My friend Evan, talking about Haskell (he convinced me to try it, at least).
• The language-of-the-month club is incredibly time-consuming. It took forever to get really basic stuff down in a new language (and I even had the benefit of having already coded some in OCaml).
• A good book makes all the difference. I highly recommend The Craft of Functional Programming. It's a great book, even if you've already been programming in other functional languages.