While teaching malware analysis courses I often get asked for good reverse engineering and malware analysis resources. This is a small collection of websites and documents that I regularly use and that I recommend to new and experienced reverse engineers.
PE file information
https://github.com/corkami/pics/blob/master/binary/pe101/pe101.pdf
https://github.com/corkami/pics/blob/master/binary/pe102/pe102.pdf
https://github.com/corkami/pics/blob/master/binary/pe101/pe101-64.pdf
And other resources at https://github.com/corkami/pics
x86 instruction set reference
Miscellaneous
https://msdn.microsoft.com/en-us/
https://hex-rays.com/products/ida/support/idapython_docs/
https://www.aldeid.com/wiki/PEB-Process-Environment-Block
https://github.com/gchq/CyberChef
Books
Practical Malware Analysis
The IDA Pro Book