A common problem many people have been running into when creating Silverlight 1.0 projects is creating reusable controls, and for that matter using Silverlight's Downloader object in a clean fashion.
Here's a simple example that I threw together for some folks internally that's a great intro to object-oriented Javascript and general tutorial for using the Downloader while avoiding global event handlers.
New in the Silverlight 1.0 Alpha is function addEventListener on elements which allows functions to be added as event handlers instead of method names.