I have a set of Conti Ultra Sport II with blue stripes in 700x23, and plain black in 700x25. Great riding tires for the money, reasonably low rolling resistance even at lower pressures, good ride feel on every surface I've tried. Very durable -- I even use 'em on my Cycelop trainer, no excessive or premature wear. So I don't need to switch tires or wheels between indoor trainer sessions and outdoor rides.
At the moment I have a set of Conti Grand Prix Classic skinwalls on the Ironman. Good tires, great looking, but they don't ride any better than the Ultra Sport II.