Python
Ruby
PHP
Pearl

Extension/embeddable languages

HeY - beos native scripting
Lua
Tcl
ECMAScript a.k.a. JavaScript, JScript

Shell script

Bash

Here is Advanced Bash Scripting Guide http://freshmeat.net/projects/advancedbashscriptingguide/ - most of it works on BeOS too (and i guess all would work with updated bash version :).

Text processing languages

Awk
Perl
Sed
XSLT

.NET

Portable.NET provides a set of tools to compile and execute applications for the Common Language Infrastructure (CLI), which is often referred to as ".NET". Portable.NET includes a C# compiler and runtime with core libraries. The Common Language Infrastructure allows the system a standard way of running any supported programming language including scripting languages and using and sharing code libraries without having to re-write them in each specific programming language.

Links:

Scripting - http://www.beosbible.com/bos/ch_scripting6.html
this link doesn't work; here's another [[http://web.archive.org/web/20030227220447/http://www.beosbible.com/bos/ch_scripting6.html]]

Here are a few more script pages:

Scripting the BeOS http://www.birdhouse.org/beos/byte/08-scripting/

from BeNews [[http://web.archive.org/web/20010220161317/http://www.benews.com/story/2188.1.html]]

and the newer hey documentation will have some information, too, as some of the above links are a bit outdated (seems the hey functionality has increased since then, i.e. I think you can execute commands now with hey)