A few more ideas:
Java, with a free IDE such as Eclipse
scripting languages such as Javascript or Python
other children's programming environments (Karel springs to mind, though maybe a bit old)
children's books for languages and resources mentioned in this thread (they are out there)
Khan Academy
IIRC one can also program Mindstorms in different languages including Java and C/C++. The built-in drag and drop programming environment is somewhat similar to Scratch, and I think both of them would be a little basic for an advanced ten-year-old, though there's certainly no harm in trying them.
