With out a doubt the ScanSnap S510 (may have a newer model now) I scan everything in my scanner. I am sick of filing and want everything at my finger tips. It is very fast, and if you do a lot of scanning, it can't be beat. Go on Amazon and read reviews. It is not cheap though, but don't go for the cheaper one. I did, and wound up buying the auto feeder more expensive one after. (I take the other one with me when I travel) but my ScanSnap S510 sits right next to me computer, and I would never be without it now. Use it continuously every day. Zip, zip, zip
I didn't buy it on Amazon (unusual for me) cause I found it cheaper at a couple of other places.