Yarra Valley is a day trip outside of Melbourne, featuring most of the area's vineyards. I went here a few months ago with Cafebus tours. Their bus has it's own espresso machine, so you could drink as many lattes and flat whites as your wanted all day. Our tour included several wineries, a dairy, chocolate shop, and lunch. We also got to play some lawn darts at one of the stops. Below are some pictures of the day.
Cafébus does tours on Wednesdays, Fridays, and Sundays. You can book on their website, or through one of the many tour booking agents in Melbourne.