I use Ransen software and love it. It automatically crops for you and you can lay multiple cards on the scanner bed and with one scan pass straightens and aligns them. You can also select a border like what you are asking for and it applies it automatically. My default is what you see on the scan below. You can select any color you want and change the size of the border. You can download it and try it for a couple of weeks for free.
http://www.ransen.com/RansenScan/default.htm
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