What are some helpful guidelines and/or best practices when branding multiple applications (could also apply to web sites) without just making them all look the same.
Edit: The original question probably wasn't clarified enough. Everyone looks at an Adobe application and knows its by Adobe. Google and Apple achieve this as well. What are some commonalities that help give consistency to suites of applications or groups of web sites besides using the same fonts, layout, etc? Or is it that basic?