Various Technologies in Speech Recognition

I would like to provide Speech recognition to my ASP.NET Web Application.

I am confused with the following five references and their documentations. I appreciate any deceleration or short explanation for each.

http://www.microsoft.com/en-us/download/details.aspx?id=24003

http://www.microsoft.com/en-us/download/details.aspx?id=10121

http://www.microsoft.com/en-us/download/details.aspx?id=10208

http://www.microsoft.com/en-us/download/details.aspx?id=35463

http://archive.msdn.microsoft.com/nesl

Beside those five, there is the (System.Speech) Namespace that is available as a .NET library in ASP.NET/Windows application, but not in Silverlight. Is it one of the above references?

Note1: Silverlight 5 provides the ability to use In-browser elevated trust application as described here. That's why I thought it is possible now to run the speech recognition on the client side instead of using web services.

Note2: I prefer to have the ability to dictate text, not only say pre-defined words.

Any further advices to achieve my goal will be appreciated.