Today Google announced that presentation sharing and collaboration capabilities is finally available in Google Docs (Google Docs & Spreadsheets is now renamed to just Google Docs). On the official Google blog, Attila Bodis writes "The new presentations feature of Google Docs helps you to easily organize, share, present, and collaborate on presentations, using only a web browser". Presentations is now also part of Google Apps.
In June Google already announced the plan for adding presentations to the Google Docs family after the acquisition of Zenter in June and before Tonic Systems in April. The Google Apps suite is now complete!
Here´s a video on the new feature in Google Docs.