>  > What about Io? I haven't used either Io or Lua myself, but they both
>  > seem to offer similar embedding-oriented features, and Io seems like a
>  > more attractive language to work in.

Io is, at this point in time, too immature, compared to Lua or Ruby.
Their current "stable" release won't even compile.
And, unfortunately, their developers are a tad insane and use darcs for
revision control, which means you can spend almost an hour retrieving
their current unstable release the first time you check it out.