Day trips are available from Melbourne, but we'd recommend a two- or three-day getaway to escape the city and fully appreciate settling back at some cabins, a bed & breakfast or even an on-vineyard hotel. Staying in wine country will not only be safer after sampling some varietals, but allow for a more thorough country experience.
Many of the traditional harvests are highlighted, including some of Australia's finest; when talking whites, Semillon, Sauvignon Blanc, and Riesling, or, for more full-bodied tastes, reach for the Shiraz, Grenache, and Cabernet Sauvignon. Whichever bottle you decided to take home, many cellar doors will ship overseas for a fee.
If you're going to pass on the international shipping, make sure you remember the 1-liter limit to bring wine back home to the US, before you have to declare and pony up a fee. Don't also be fooled by the lower drinking age in Oz; you still need to be at least 21 years old to bring alcohol back into America.