If memory serves me correctly, I started with Java, then moved through REBOL, Python, Ruby, Scheme, and Lua before I dropped the practice. I tried getting back into it with Haskell a few years ago, but didn't take it to the "ok, I get it now" level of proficiency--mostly because of time constraints of changing jobs rather than any issue with the language.
I did learn something from each of these, which is the real point of the exercise. Now I'm thinking about starting a (belated) Language of the Year for 2010. The contenders are:
Pro: interesting concurrency (independent processes) and data (immutable) models.
Con: might be too big to get my head around in nights and weekends
Pro: Small surface area; looks like "Lua with a prototype-based object model" so far; might be useful practically.
Con: Not sure there's enough new there after doing Lua and REBOL.
Pro: Interesting transactional memory model. Also, .
Con: I'm wondering how much time I'll spend re-learning the Java environment vs. learning Clojure.
Pro: Interesting concurrency model; might be useful practically.
Con: Not sure there's enough different there, compared to Clojure or Erlang.
Part of the problem is picking a language that different enough to make it worth learning, but not so different that I can't use it for small, practical tools that I can actually use day-to-day. The Haskell and Scheme experiences showed me that if I can't use what I'm practicing day-to-day, I find it hard to keep devoting time to the project.
At the moment, it's looking like Clojure > Go > Erlang > Io. I'll probably pick up a distribution for each, get as far as "hello world", and then decide.