If you're using SSMS 2008, there is another neat trick. In the Registered Servers panel, make separate folders for each logical (to you) group. Then, you can right-click the group, select "New Query", and a query window opens up connected to all of the servers. Run something like "SELECT @@ServerName", and you'll get responses from all of the servers.
Wayne
Microsoft Certified Master: SQL Server 2008
Author - SQL Server T-SQL Recipes