Where can I sell wine on the Internet?!

There's WineBid.com, but they prefer to deal only with larger sales, $2,500 and up. Your case of Opus One 1985 may be worth that much; you'll have to complete their consignment form to see what they think. But they do it on consignment, which may make it easier to deal with local wine regulations.

WineCommune.com is more of an eBay like seller-to-buyer situation, so they deal with smaller lots, but you'll have to deal with the (tortuous) shipping regulations yourself unless you use them for consignment.

If you're asking this question, you probably have no history selling wine. If that's the case, no one will buy your wine, since you can't guarantee your selling history and also most likely can't guarantee ideal storage conditions. 1985 was a decent vintage for CA Cab, but you're going to have to be prepared to take much less than you think the wine is worth.

Drink up!

I'm a sommelier.

There are several specific wine auction houses (such as www.auctionvine.com ), but those are usually business-buyer, not private seller-buyer. A better solution is to sell on eBay, which is easy and will guarantee results, as this is the largest auction house around.. In addition, publish on as many wine forums as you can, because it's a special item after all.

Search google for "wine forum" without the quotes, and simply list out ebay link.
You'll most likely find good buyers on eBay alone, but additional links can help.

you can't sell wine or other alcoholic beverages privately in most of the world

your only choice would be to contact a local reseller, auction house, or properly licenced company.
you likely will also only be able to sell to a small area, likely your state... and possibly a few others. alcohol laws in the US vary by state

it may very well be illegal to buy wine on the internet because there is no way to prove the age of the purchasing party. You could try it on craigslist or ebay, but to avoid legal trouble, ask for a fax copy of their ID (maybe two peices of ID to be sure).

1985 Opus One has been averaging $159/bottle selling price, according to WineBid.
For such a valuable wine, and depending where you live, you might consider offline options such as Christie's and Sotheby's.

Another good online option is Chicago Wine Company.

ebay, is a really good place for selling you items!