Lisp + Emacs + Slime felt like a total joy to me. Python with its REPL and a "batteries included" approach was a distant second, with Perl (with emacs' cperl-mode integrated with perl's debugger as well as the extensive and easy to use CPAN library) being a closed third.
I might also get branded heretic for saying this on HN, but lately I've been also able to enjoy Java development: with git for revision control, maven for project lifecycle management/pulling dependencies in an almost CPAN-esque manner, IntelliJ for an IDE (which, I've been told comes close to the capabilities that the Lisp machines had as far being an IDE goes) and jetty (invoked through maven) for a servlet container (a breath of fresh air compared to Apache as well as tomcat).
I'm enjoying my time with maven/jetty too. It was a steep learning curve but once it works its very smooth. I also recently substituted Java for Scala and can recommend that highly if you're doing the coding for the fun of it.
I might also get branded heretic for saying this on HN, but lately I've been also able to enjoy Java development: with git for revision control, maven for project lifecycle management/pulling dependencies in an almost CPAN-esque manner, IntelliJ for an IDE (which, I've been told comes close to the capabilities that the Lisp machines had as far being an IDE goes) and jetty (invoked through maven) for a servlet container (a breath of fresh air compared to Apache as well as tomcat).