While thinking about how to keep track of various configurable application settings in the X10 application, I came across
an article in MSDN Magazine from October about a match-making game. The author referenced a previous article where he talked about user and application settings and how to store and retrieve them. Following his links, I came across an article from Emad Ibrahim that explained
the easiest way to keep track of settings in Visual Studio 2005 - it's built in!
First, here's my current list of simple properties:

So in the project properties, I have defined these settings under the appropriately-named Settings tab:

As you can see, you just specify the name of the property, the type, whether it's user- or application-level, and the default value. Simple. Then, you can even tie controls on the form to specific settings! Under the properties for a control, such as a checkbox, you see this:

You just click on the box next to Property Binding to bring up a box allowing you to bind control properties to application settings:

I want to bind the checked property of this checkbox control to an application setting. Clicking the dropdown on the checked property shows the various application settings I've defined:

The checked property is automatically set during startup based on the application setting, and the settings file is automatically updated when the checked property is changed by the user. It's like magic.