http://mediaspark.com/filters.htm has some free filters that MAY work for you, but probabaly you would be happier with using a feathered selection, and airbrushing out the edges. You probably know this already, but if you select all, then from the selection dropdown, you can choose MODIFY/BORDER, and that will give you a feathered frame selection around your canvas. Or, you can make a layer above, fill it with your canvas color, erase out over your focal point, then blur... just a few ideas, there are probably hundreds of ways....