Jani Jarvinen (a Finnish C# MVP) wrote a nice article about using sensors with Windows 7. He mixes and matches .NET 4.0 and Code Pack capabilities, and has links to plenty more information. I like the screenshots and the step by step approach. Windows 7 really does make this so much easier than it used to be. He gets you started with both an ambient light detector and some simple location code.
A little more exotic approach comes from "gleat" who has a Code Project article using a Wiimote as the accelerometer. He starts out simple - here's how to download and install the driver - and then goes into writing a client in C#, leveraging Code Pack of course. But then he says hey, were you wondering how to write a driver? and wham! you're hip deep in C++. It's all well explained, though, so if you want to learn more about this, what a terrific way to start.
If all of this is making you wish you had Windows 7 somewhere to play with, but you don't want to buy it, don't have an MSDN subscription, don't qualify for BizSpark etc, then what you need is a free 90 day evaluation of Windows 7, right? I found that link on this handy Doug Turnure blog post from earlier this year that includes some video links I hadn't seen before. Have fun!