Which are your favorite windows forms books/blogs/websites? (I don't think this is a dup...have checked other related questions)
I usually check www.windowsclient.net it has resources for both WinForms & WPF
http://www.syncfusion.com/faq/windowsforms/default.aspx
This helped me a lot when i was new to winforms (disclaimer: that was a long time ago, in a galaxy far, far away... so i don't know if it's still up to date).
I've found Windows Forms 2.0 Programming by by Chris Sells and Michael Weinhardt to be very useful.
The site indicated by Teodor really helped me out back in 2003 when I started studying/using Windows Forms.
If you're really into Windows Forms you should really take a look at data binding and there happens to be a book on this specific topic.
Data Binding with Windows Forms 2.0: Programming Smart Client Data Applications with .NET (Microsoft .NET Development Series) Author: Brian Noyes ISBN: 032126892X
I've seen a lot of people saying bad things about data binding only to reinvent the wheel in a worse way. I highly recommend reading this book for that matter.
It would be know how the CLR works first
CLR via C# by Jeffrey Richter
Programming .NET with C# by Andrew Toelson ( APress ) a very good book
Programming Windows Forms - by Charles Petzold
Book: CLR Via C#. Hands down best C# book evar. I just recently dusted it off to help me understand how to work with multiple appdomains to keep different versions of the same assembly separated.
Websites: Here, lol; dotnetkicks.com (standard disclaimer here), and codeplex.com. Codeplex is THE place to store your code, folks. If you're working on something and you don't need to keep your code private, create a project on codeplex and use it for source control. That is, unless you're a svn guy, in which case use code.google.com or one of the other free online svn control providers.
Blogs: CH, of course... the Gu, the Haack, Hanselman, Cazzulino... I've got a big blogroll at work, but these are the ones I remember with the most and best info.