Finder freezes after updating to OS X 10.10.4
In my case it helped to remove the application state of the Finder. This command will move the state file to your desktop:

mv -r ~/Library/Saved\ Application\ State/com.apple.finder.savedState ~/Desktop/com.apple.finder.savedState


Then restart the Finder process with killall Finder. If that was successful and you don't need anything from the old state file on your desktop (like a list of the opened windows from the last session), you can move it to the trash.