For version for SharePoint 2010 press here
Cross View Web Part allows cross-site and cross-site collection queries and displays results as standard SharePoint view.
The web part allows aggregate data from:
· Multiple lists on the same site
· Sub-sites or entire site-collection
· Cross site-collection queries (Professional version only)
The web part contains rich set of query definitions, grouping and sorting options.
1. Display all incomplete tasks from all projects where Due Date < Today and group by Project Name (Site)
2. Display all active Quotes from all sites in the entire site-collection where Quote Amount > $2,000.00