I deal with a lot of folks that are going through server consolidation exercises. These days everyone immediately thinks of Virtualization - which will consolidate servers onto a single instance. But in many cases it's actually smarter to evaluate the load across your servers and then "stack" databases onto one instance, or even install multiple instances on one SQL Server.
Along the way, it's probably a good idea to dust off that data archival project you started a while back. By controlling the data you have to store, maintain and backup, and wade through for your application, you can consolidate even further.
There are a lot of ways to do this, and there are a lot of ways to protect the data when you do. Make sure you check out Data Protection Manager and SQL Server. More here: http://msevents.microsoft.com/cui/WebCastEventDetails.aspx?culture=en-US&EventID=1032322231&CountryCode=US