This is a Q & A question for people (especially ISV's like us) who deal with lots of different orgs.
It's often critical, in a single screen (like a managed package install process) to be 100% sure which org you are dealing with. You can look at instance name, or go to your org or user details page, but instance name isn't specific enough when you deal with dozens of orgs, and the org/user details pages are a click away.
So, how do you manage this?