Just upgraded one of my clients' osCommerce sites to the latest suggested patch that kymation posted... However, I didn't get any results for domestic shipping... :/
My client only wanted to offer "1st-Class Parcel" and "Standard Post" for domestic shipping options. I saw the note above that Standard Shipping was only for live animals (WTF?), so I disabled that option, but no luck.
When I enable all the domestic shipping options, only then did I get Media Mail, various Priority Mail, and various Priority Mail Express results. Convinced my client to add "Priority Mail" to their list...
I also noticed that the transit times aren't being shown anymore, and there isn't a config option to turn it back on -- was this removed/disabled for some particular reason?