
Autodesk User Group International has posted a nice article of tips on Script Files Customizing AutoCAD written by and AutoCAD Guru and also one of the most experienced and feedback providing AutoCAD customers Lee Ambrosius.
Lee also has a blog for many great tips on AutoCAD titled "Beyond the UI".
http://hyperpics.blogs.com/beyond_the_ui/
Cheers,
-Shaan