How Can I Get US Pictorial Postmarks On Covers?

I enjoy producing commemorative covers using my own PC and printer (like the one illustrated)

. In the UK, the Royal Mail make things easy as they produce a bulletin listing all pictorial and commemorative postmarks to be issued, giving a few weeks advance notice for each. I can then send stamped covers to one of five regional handstamping centres to obtain the relevent postmark.
Do such postmarking centres exist in the USA, or is there a different system for postmarking franked covers? I have written to the US post office on a few occasions asking for information, but have yet to receive a reply.
Any information would be appreciated.

Here's a link to the US Postal Service's Postal Bulletin for December 29, 2011. It comes out bi-weekly. The next issue is due out on January 12, 2012:

http://about.usps.com/postal-bullet.../pb22327.pdf

If you download these Postal Bulletins, then select the Stamps/Philately Section, it will provide you with the latest update of new issues scheduled for release, as well as a list of pictorial cancels announced in that timeframe, along with instructions for requesting them. The service is free, you only need provide them with self addressed stamped envelopes (with US postage, of course) and an oversized return envelope with appropriate US postage for the safe return of the covers.

Typically, pictorial cancellations are available for 30 days after the date of the event; some longer for as much as 60 or 120 days, depending on when the announcement was first made.

Wow! Thanks for this link. So much valuable information!