A couple weeks back they launched a free app of the week promotion, and news coming out today suggests that they're going to capitalize on the effort. MacRumors noticed today that Apple owns a couple new website addresses.
They're not pointing at anything yet, but according to a whois lookup both www. freeonappstore.com and www.freeonibookstore.com both belong to Apple. It seems to me that Apple might be planning to use that link to promote free or temporarily free ebooks and apps.
The websites were registered during the WWDC, but as we all know from watching the news reports of that event, Apple didn't discuss anything about new sales promotions. We don't really know what Apple plans to do with them, but I'd say it's pretty obvious.