C# is very similar to Java language. So if you are a Java language expert it hardly takes a week to learn C#. Here are a list of free C# (csharp) books I was able to find on the net. Unlike Java there aren’t many good quality free books on csharp. Let me know if you know of any good books not included here.

1.Wiki book on Csharp programming -  A work in progress.

2. Sams Teach Yourself C# in 24 Hours - This is in HTML form and hence downloading is a pain.

3. Vijay mukhi’s csharp basics. HTML book can be downloaded as a zip file.

4. Data Structures and Algorithms with Object-Oriented Design Patterns in C# by Bruno R. Preiss - This is a bit old (2001) but still useful.

5. Programming the .NET Compact Framework in C# -  Can downloaded as PDF. Focuses on .NET framework.

6. Dissecting a C# Application: Inside SharpDevelop - This looks at SharpDevelop IDE and its source code.

7. C# in detail by Jon Jagger - Can be downloaded as a zip file.