I tend to use SQL Server Management Studio also for quickly doing stuff, but when I am doing the actual implementation or more advanced stuff I use EMS Sql Manager. It is quite a nice tool with far more advanced and more numerous features than Sql Management studio. You can think of it as MS SQL Management Studio on steroids. Takes a bit of getting used to the UI though, but still straight forward enough. And if you get their package with all their peoducts you get a ton of great utilities as well.
If its just diagramming thoguh i will use Visio.
