Recently I dropped by the Taiwan Wine Cellar (go here for the address, a map and other details), a shop in central Taiwan that sells locally-produced wines and spirits. Opened in 2008 by Erlin Township Farmers' Association, it has an impressive range of alcoholic drinks, including liquors made from passion fruit and pineapples. Connoisseurs of good European or New World wines are unlikely to find anything to anything that pleases their taste buds, but if you're looking for liquid souvenirs of your time in Taiwan, this shop is a good bet.
Changhua County's Erlin Township (彰化縣二林鎮) is said to have the highest concentration of wineries in Taiwan; the staff at the Cellar told me there are 19 legal wineries in the area, a legacy of grape-growing on a large scale for sale to the government's Taiwan Tobacco and Wine Monopoly Bureau. When Taiwan joined the WTO in 2002, the monopoly was abolished and the bureau converted into a state-run enterprise, TTL. Because TTL now sources its grapes from elsewhere, Erlin's grape farmers have began making their own wine.
There are wine producers elsewhere in Taiwan. One I've visited, and whose products I like, is CJ Wine Village (藏酒休閒農場) in Yilan County.