Where can I get information on hosting Windows Forms Controls in IE?
These articles should give you some introduction to hosting WinForms Controls in IE: Using Windows Forms Controls in Internet Explorer Host Secure, Lightweight Client-Side Controls in Microsoft Internet Explorer
What are some things to remember when drawing in Window Forms
Check out the Painting techniques using Windows Forms by Fred Balsigerat gotnetdot.com. It is a good basic discussion of how to get the best performance from Windows Forms drawing. His hints include leveraging the power of the .Net Framework by using the proper controls and control styles as well as consolidating painting code in the OnPaint and OnPaintBackground methods.
How can I add an icon to my menu items
You need to implement an owner drawn menu to add icons to it. Take a look at the sample on .netPlus.
Are there any easy to use Unit Testing frameworks available for .NET applications?
There are several. Here are a couple of systems that we like. They use .NET debugging support seamlessly and are thus very painless to use. You have no excuse not to write Unit Tests anymore! NUnit
How can I simulate keyboard input in my application
This can be done through the SendKeys class in the System.Windows.Forms namespace. Check it out in the MS help documentation.