I use PopClip (http://pilotmoon.com/popclip/ http://pilotmoon.com/popclip/) on my Macs. It's not quite as seamless as having everything you select automatically

I use PopClip (http://pilotmoon.com/popclip/ http://pilotmoon.com/popclip/) on my Macs. It's not quite as seamless as having everything you select automatically available for middle-click pasting, but it's pretty close.