For (1), I picked up the book Seven Languages in Seven Weeks and learned to write (really basic) Ruby, Io, Erlang, Prolog, Scala, Clojure and Haskell. I didn't write anything great, but it was a lot of fun to play with new ideas.
For (2) I decided a couple of weeks ago to implement my own Lisp. I know almost nothing about Lisp and so I'm making a lot of mistakes and re-inventing the wheel a lot, but having a language whose syntax or semantics is changeable on a whim is just so much fun. Want a syntax for function literals? You can add it. Always thought that hashmaps should be a special case of functions? You can add that too. I can't recommend this enough as a way to rekindle your interest in computer science. I'm going to work on the language in my spare time for a couple more weeks, and then try to write a compiler for it. I've never written a compiler before (I was a math major, not computer science). I have no idea how you do it. But I'm pretty certain it's going to be fun.