Despite the buzz surrounding Internet-based phone services like Skype, most Americans still have regular phone numbers. With VoIP, callers can take advantage of free calls around the world to other online contacts, plus ultra-low rates to regular numbers. So why not combine the best of both worlds and make all your calls from a single handset? That's where dual-mode phones come in, which let you flip back and forth between regular lines and voice chat clients at the touch of a button. The only caveat: These low-cost systems must be connected to your PC's USB port to work. We tested five models: Two support Skype, two connect to Yahoo Messenger with Voice, and one delivers voice calls through Windows Live Messenger. Read on for the results.