Dont know if you can get the cost of carry at some particular site... Guess you will, but dont know where. Its pretty simple to calculate anyway using the futures pricing method... As for a range, after accounting for any dividend payments, a decent CoC would be between 5-10%. Anything lower would mean portfolio insurance/ shorting, and a substantially higher figure could indicate a buying frenzy in futures without adequate buying in the cash market. With many mutual funds coming into the arbitrage arena, the instances of high cost of carry could disappear... depending of course on the corpus of thee fund.
Its always better to look at the cost of carry in a historical perspective to decide whether the CoC is too high or too low.