SharePoint Online is a new service available from Microsoft: It's SharePoint, but hosted by Microsoft. SharePoint Online is a key part of the Microsoft Online Services stable.
One of the concerns often raised to me about SharePoint Online is that "you can't do much with it at the moment". This is understandable, because although SharePoint Online is based on MOSS 2007, it is in reality a very locked down version of it. For example: no custom code.
However at Thinkscape, my employer, we are finding that the locked down nature of SharePoint Online is not a blocker to building creative business applications. As early adopters and specialists with SharePoint Online we have been quick to find out ways around the apparent limitations. For example, by using Silverlight for advanced user interfaces.
We are now looking at integration of SharePoint Online with on-premises SQL Server Reporting Services and front-end ASP.Net websites. The potential applications are quite limitless.
We have published a video of a solution we built for SharePoint Online on our website, shortly to be included in Microsoft's Partner Solution Showcase. The video should help provide an insight in to what you could do.
Check it out here: http://www.thinkscape.com/Telemarketing-Solution/