Over at scribd.com, an online library site, someone’s posted the full SimCity manual for viewing. On page 8, under ‘SimCity Store’, the following can be read:
Click the banner on the main menu to enter the SimCity Store. Here, you’ll find special add-ons for sale. Select STORE to view the full list or additional game content (both free andpaid) that can provide you with new gameplay possibilities.
Keep checking back as we learn more.