In an ongoing project of mine, I needed access to a good source of information that is free, powerful and provides some sort of API. My first thought was on Wolfram|Alpha, a powerful search engine that have thousands of databases filled with useful information and a really great interpreter that tries to guess what you mean by the 22th president of the USA. If you have not yet tried Wolfram|Alpha, I highly encourage you to take a look at it.
The results from Wolfram|Alpha when looking up "Google stock"
Wolfram|Alpha has a REST based API that outputs beautiful XML data ready to parse. They really put some work into making it easy to use, so I though it would be a no-brainer to find an existing C# library that would parse it and give me objects that I could work with. However, it turns out that there are only a few of them, and only a fraction of those support the 2.0 API that Wolfram|Alpha introduced back in January 2011. I decided to code an API myself that could be easily extended with new features and would provide me with the full API.
I present to you, the all new WolframAlpha.net API. It is based on the open source RestSharp framework for parsing the XML data, so a big thanks goes out to the guys behind it for an awesome job.