Dynamic database reference in T-SQL scripts

The answer is Synonyms.

Repeat for each database in foo family:

create synonym bar for [srv-db].<bar-db>.dbo.bar;

And then use it as follows:

select f.*, b.* 
from foo f inner join bar b on f.barid = b.id ;

Synonyms and dynamic SQL are both solid answers (although you can't use dynamic SQL within a view). If you are using Visual Studio to manage your database projects, there is another route open to you: database variables. If you have database projects named foo and bar and configurations Debug, QA, and Release, you could use an app.config transform (perhaps using a tool like Slow Cheetah) and on deployment, the correct database reference would be used and a later DBA wouldn't get confused as to what "foo" means in that context. Synonyms aren't very commonly used in my experience, so they are something that one could easily overlook.