Google has recently unveiled Google Open Gallery, created as part of the Google Cultural Institute. It allows users to create online exhibitions, in the manner of Omeka. It is targeted at museums and galleries, and has already partnered with the Getty and LACMA; however some of the sample galleries on their site have been created by artists, collectors, and fans, and it clearly has value for classroom projects. In addition to allowing users to create online curated collections, it offers enhancements such as image zoom and term search features.
Read more about the initiative in the LA Times.