SharePoint 2010 supports:
300 content databases per web application
250,000 site collection per web application.
10 application pools per web server.
Size of content database can be 200GB.:
In case of document archive scenario there is no limit on content database size.
There can be 60 million items including documents and list items in Content database.
SharePoint 2010 recommended 2000 site collections per content database, but that can be maximum of 5000 site collections.