There are currently many listings for Antiques Roadshow tickets for the 2009 season. However, at least one thing has changed this year, and should concern prospective buyers.

Antiques Roadshow is actively checking on ebay, and can (and will) cancel tickets that are being resold, as that is a violation of their rules. I know this for a fact, as I know a person who had theirs cancelled.

NOTE:

• These are being cancelled by Antiques Roadshow, not ebay. So the listing may continue to completion, and the seller may not tell you (if he's not the original owner, he may not even know). 
• Antiques voids the ticket numbers, so the tickets will not work when you try to enter the event. You cannot tell by looking at them that they are worthless, as the only correspondence is an email from Antiques Roadshow staff to the original ticket holder.
• If you attend the event with a voided ticket, you'll be stuck at the turnstile with entry denied.

If you have already purchased tickets, good luck. I hope they work for you. You might want to contact Antiques Roadshow to verify the numbers are still valid before making the trip.

6/1/2009: Directly from Antiques Roadshow spokesperson:

"ANTIQUES ROADSHOW's ticket rules clearly prohibit the sale of our tickets......" and

"When we are able to track down the name of a seller or the ticket numbers offered for sale, we
cancel those tickets and they are no longer valid for admission to a ROADSHOW event."