I don’t know any free source. TED spared is not that difficult to compute (take 3-month U.S. dollar LIBOR, subtract the 3-month U.S. T-bill rate, and you’re done), but British Bankers Association makes available for free only a limited rolling window of LIBOR data (six months ending two months before the beginning of the current month). For example, right now, the only are for September 2010 through February 2011