I am looking for a good Extensions library (library with a great number of extensions methods) in C# for standard type. I have found some libraries on Codeplex, but they are considered to be very weak by me.
Edit: I need a library which implements different mathematical functions for different (more the better) purposes.
You could check the Extension Overflow project on Codeplex, which was born from this post.
Otherwise, if you are looking for a math library, have a look at C# Programming Tools on MSDN. I don’t know if the math libraries there contain lots of extension methods, anyway…