Acrobat.com is Adobe's software-as-a-service initiative and it went live recently. The presentation tool is still in beta but can be tested here.
I am making a (small) u-turn on all these in the cloud office tools. A recent shift to part-Mac/part-PC working has showed me that (unlike spreadsheets and databases) the learning curve for working with a new presentation is actually not that high. Let's whether either Adobe or Google docs can take on Microsoft's dominant position in office software. I am less optimistic about the changes of completely new startups trying to do the same thing. Especially given that Microsoft will come with its own in-the-cloud offering with a user interface that is very similar to the desk top version.