Anthony Hawkins' Wine Reference Material Searchable glossary provides information about hundreds of types of grapes. Also contains vintage charts and tasting note terminology.

De Long's Wine Grape Varietal Table Offers information about 144 varieties organized in an interactive table. Also sells a print version of the table.

Enjoying Viognier Features news and information about Viognier, a wine of the month, and a searchable database of retailers and prices.

GrapeSeek Searchable collection of links, including grape variety and viticulture resources.

P.S. I Love You Industry organization dedicated to promoting the Petite Sirah grape. Includes a history of Petite Sirah, articles, a list of members, and recipes of suggested food pairings.

Pinotage Association Association promoting South Africa's Pinotage. Contains a history of the grape, winemaking information, and a producer list.

The Zin Zealot Focuses on Sonoma County Zinfandel. Includes links to information about the grape, tasting notes, and a list of wineries.

Wine and Juice Grape Varieties Information about varieties suited for cool climates.

Zinfandel Advocates and Producers Non-profit organization dedicated to promoting Zinfandel. Contains information about the grape, membership details, and a list of events.

ZOW - Zinfandel on the Web Contains tasting notes and links to Zinfandel-producing wineries.