My favorite thing about Lua is that it trivially builds anywhere with a C compiler. Lots of other languages that bill themselves as "embeddable" are a real pain in the ass to build on weird platforms.
Fun example: there's a project (Lunatik) that embeds Lua inside the Linux kernel, where no userspace C APIs are available. You'd expect that would require extensive patching but they mostly just had to tweak the makefile and a configuration header file.
