Earlier this year Microsoft launched SharePoint Online, which is part of its Office 365 product offering.  As with an on-site deployment of SharePoint, you can create sites and lists, share documents, etc.  However, SharePoint Online simplifies it all by removing the need to deploy, configure, monitor, update or upgrade an installation on your premises. You can use the Online Services Administration Center to create new sites, install solutions, and provide access to specific users.

Small and medium-sized businesses can now take advantage of the same enterprise-grade technologies that are available to larger companies, without having to take on the operational and hardware infrastructure necessary to host SharePoint on-site.

A common mis-conception about using this product concerns custom development.  SharePoint Online does not change your ability to customize your environment so that it meets your business needs.