There are a few vineyards and I can''t remember the name of all of them, but find them -- it''s worth it. You can arrange a tasting, which is fun, and a tour which can be interesting.
Vin Santo is a sweet desert wine, and you can dip biscuits into it, or drink it chilled to round off a good meal. Vedema (meaning "harvest") wine is a general table wine, so it will be cheaper. Generally, Santorini wine is difficult to find once you get home so bring some bottles back with you.
When you''re done you can make yourself a Bellini, peach juice and Santorini sparkling white wine -- fantastic, aah! For information and a tour here is the telephone number: +30-22860-81607.