Dallas has the 80C320 which has two serial ports. And then if you wanted to step up to new technology look at the Cygnal parts at www.cygnal.com. Many of the Cygnal parts such as 'F020, 'F021, 'F022, 'F023, 'F040, 'F041, 'F042, and 'F043 plus others sport 2 UARTs.
Michael Karas