Some of the key features of successful scripting languages are:
Unix scripting languages can be traced back to venerable tools like sh (for shell scripting), sed (for stream editing) and awk. From here, emerged fully blown scripting languages such as TCL and Perl.
Perl 5 offered object-oriented programming support, while there are a number of unofficial OOP extensions for TCL.
The GNU's "official" scripting and extension language is guile, a Scheme implementation.
Python built on languages such as Perl and TCL, as well as ABC, Modula-3, C and sh.
Ruby is a relatively new scripting language from Japan that borrows heavily from Perl and Python.
There are a large number of other scripting languages on the fringes: Lua, Rexx and Rebol are probably some of the more well-known ones.