I have a little game written in C#. It uses a database as back-end. It's
a trading card game, and I wanted to implement the function of the cards as a script.
What I mean is that I essentially have an interface,
public class Card056 : ICard
ICard Cards[current] = new MyGame.CardLibrary.Card056();
Oleg Shilo's C# Script solution (at The Code Project) really is a great introduction to providing script abilities in your application.
IronPython and IronRuby are both available today.
For a guide to embedding IronPython read How to embed IronPython script support in your existing app in 10 easy steps.
Lua is a scripting language commonly used in games. There is a Lua compiler for .NET, available from CodePlex -- http://www.codeplex.com/Nua
That codebase is a great read if you want to learn about building a compiler in .NET.