This article outlines Google’s plan to give your Google Apps’ account (e.g. firstname.lastname@example.org) the ability to access other services (e.g. Picasa web). The plan is *not* to merge existing Google Personal accounts registered under that email address.
Google will automatically create regular Google accounts for Google Apps addresses like email@example.com, so you can use the same credentials to log in to Google Apps services (Gmail, Calendar, Docs) and Google Accounts services (Google Reader, Blogger, Picasa Web Albums).