This is a Dutch article I wrote on the use of symmetric and asymmetric encryption techniques in .NET. It's not revolutionary, and probably you've seen numerous examples. But if you haven't, you may also want to check out the sourcecode so you can play with it yourself. Here's a screenshot:
The keysizes are fixed in this example, but there are easily modified if you want. When you do so, I'd recommend this page, to calculate how long your key length will protect your information. The location of the public and private keys is selectable, so you can take the private key with you on a USB stick if you want.
[update: since I've upgraded Technolog to Community Server, I needed to change the links in this post.]