Organic wines and sulfate-free wines are a step in the right direction but often, the biggest eco-challenge with wine is not the wine at all, it's the bottle. A bottle of wine is heavy and if it comes from far away, the weight will incur a big carbon footprint from transportation.
For many years, box wine was for communion and grandmothers only but these days the box is rising in status. Popular wineries like French Rabbit proudly box their goods. Replacing glass with tetra pack – even though tetra-pack isn’t yet recyclable in some locations – considerably lessens the carbon footprint of your party.
Wine is best grown in warm dry climates but even so, wineries are in production across North America. Judge your local wine by your own pallet and if it doesn’t suit you, investigate local microbreweries or cider alternatives, wheat and apples are better suited to colder climates. Buying locally will not only cut down on transport but also win you Ground Rule 4 or social sustainability (see Tracy's book, Your Green Family Blueprint for further details) points by supporting your regional economy.
If you do choose to go further afield for wine, you can negotiate your impact based on region of origin. A study by National Geographic found that East Coasters are better off buying from Europe and of course West Coasters need look no further than their own Napa Valley. Both East and West can enjoy the same bottle of Chilean wine which is shipped over water, as opposed to land or air, incurring a relatively smaller carbon impact. Check out this article on Treehugger for a more detailed breakdown - http://www.treehugger.com/files/2009/04/ship-or-truck-makes-all-the-difference-in-wine-carbon-footprint.php
In addition to reducing the carbon-footprint of the wine you are drinking, look for wines that are organically grown and/or have a strong sustainbility framework that guides their operations. Having trouble seeing if the winery does these things from just the bottle or their website? Great excuse to send them an email or pick up the phone, ask questions and let them know these issues are of importance to you!
Cheers! Prost! Skål! Salud!
Plastic is a man-made compound that nature has no way of processing or 'digesting' naturally. Because of this, it exists far beyond any single human lifespan, creating an ongoing legacy for future generations to manage: it exists in our soil, in our water and its components are released into the air when it's burned or it is consumed by sea life and animals mistaking it for food. 
