When we do need to make big enlargements of our photo files :

http://www.adobe.com/store/plugins/pages/genfractals.html Genuine Fractals by Altamira Group .

http://www.nyphotographics.com/ftppage.htm Several PS plugins to upsample photo files .

http://www.fredmiranda.com/SI/index.html Stair Interpolation by Fred Miranda .

http://www.dpreview.com/forums/read.asp?forum=1004&message=2367161 Free upsampling software .