Squeak Smalltalk: almost as good as Lisp for experimental programming
Smalltalk is an image based system - when you start up Squeak, your working environment, including data in memory, code changes, etc. is exactly the way you left it the last time you ran the Squeak system (assuming that you save your working image).
Smalltalk is not for everyone, but it is worth a try. There are enough Squeak tutorials on the web, so at least initially, spending a few evenings with Squeak will not cost you any money.