Finder doesn't work since Yosemite
Solution 1:
This fix from Reddit worked perfectly for me!!
http://www.reddit.com/r/osx/comments/2jtikj/finder_not_responding_new_yosemite_install/
You can most likely fix the issue by clearing out Finder's saved state, caches, and/or settings.
Use Spotlight (the search icon in the far right of the menu bar) to find and open the "Terminal" application. Triple-click the following line in order to copy and paste it into Terminal's window:
rm -fR ~/Library/Saved\ Application\ State/com.apple.finder.savedState ~/Library/Caches/com.apple.finder; killall Finder
If it still doesn't work, try this one:
mv ~/Library/Preferences/com.apple.finder{,.backup}.plist; killall Finder
Solution 2:
After Yosemite upgrade the finder crashes every time I drag and drop a file to a folder in the finder. It basically freezes and 'floats' the file icon until I force quit finder.
I tried quitting the Dropbox finder extension but it didn't work for me (you must quit Dropbox app first or the finder extension will auto relaunch). So I looked at the console errors right after a drag and drop crash and noticed a trail app I had trialed called Intego VirusBarrier that was causing the issue. After an uninstall and restart the finder worked as expected in Mac OSX 10.10.