I was looking for a way to copy only certain file types from one folder to another. Basically a recursive copy with a filter.
There are different solutions, but here I found the best one, that does not need any additional tools.
http://www.vistax64.com/powershell/30490-copy-item-recurse-wildcard.html
Just open the Windows Powershell and type the following command:
copy-item -rec -filter *.resx C:\source_dir C:\target_dir
This will copy all files with the ending .resx from source_dir to target_dir.
Problem solved.