Apple plans to start it's iAD on July 1:
" ... a little over one week after iOS 4 becomes available to the general public. The iOS 4 update allows developers to incorporate the service into their applications using the API that Apple offered in beta form in April. According to Apple, deals have already been inked with numerous major brands, including JCPenny, Nissan, Best Buy, and AT&T. The Cupertino company claims the deals are worth more than $60 million, which accounts for nearly 50 percent of the mobile ad expenditures for the second half of 2010 as predicted by JP Morgan earlier this year .. '
Beyond that they are working with global CPG company Unilever.