John Mayer kicks off a national tour this summer and is bringing along newcomers Colbie Caillat and Brett Dennen as opening acts. Both California-bred folk-pop artists were featured performers on Mayer's Mayercraft Carrier last month, the three-day Bahamian cruise designed to give fans the most intimate Mayer experience yet (look no further than his Borat-inspired swimsuit for proof), and were hand-picked by the Grammy-winning singer-songwriter himself. If 2007's Continuum tour is any indication, concert-goers can expect the occasional sit-in among sets as well. The trek is scheduled to start in July with a full list of dates to be announced soon.