Google starts offering its Google Apps in few packages especially aimed for companies or families/groups etc… I think it is the best for small business you can find on whole Internet.
What does this mean for my problem about inner-office system in DB Production? I start thinking about Google Apps as the base with some small extensions (for clients and projects) – probably I should use GData here… and all this will be used in our well-known Mozilla applications (Firefox, Thunderbird + Lightning) also with few extensions.