Its near impossible to find a laptop to play skyrim on medium at that price range. http://www.amazon.com/U31SD-AH31-13-3-Inch-Light-Laptop-Black/dp/B005SRZATG/ref=dp_return_1?ie=UTF8&n=541966&s=pc
that might play it on low
You can find some in the 600 dollar range that will play it on medium
your best bet is used/refurbished that has at least the GeForce GT 550M dedicated graphics card or AMD Radeon HD 7670M or better
both those cards should be able to play it on medium
finding a desktop would be a much more feasible task in that price range
edit: chudddds has a good recommendation with that refurbished on newegg, reading the feedback, a user claimed to play skyrim at 50-60 fps at high, though he says he overclocked the cpu to 2.0/2.4 ghz from the stock 1.4.