Oleg Shilo’s C# Script solution (at The Code Project) really is a great introduction to providing script abilities in your application.
A different approach would be to consider a language that is specifically built for scripting, such as IronRuby, IronPython, or Lua.
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.
A different angle altogether is to try PowerShell. There are numerous examples of embedding PowerShell into an application — here’s a thorough project on the topic:
Powershell Tunnel