NewerTech (www.newertech.com) has introduced the Snuglet, a precision-manufactured ring designed to sit inside your MagSafe 2 connector port and provide a more snug fit to prevent your power cable from unintentional disconnections.
The NewerTech Snuglet purportedly provides a greater magnetic hold, making the MagSafe 2 power connection stronger. It costs US$19 for a box of two Snuglets and one removal tool.