I use Google Apps at work and Google for my personal account as well, this means that sometimes I have to take a few steps to log in to both accounts at once. Google has tried to make it easier with the new Account Chooser.
It works by linking one Google account to the others, so when you’re signed into account #1 it knows you should have access to accounts #2, #3, and so on. Some users will see a preview link on the sign-in page when they visit it, but if you want to enable the new feature now you can just visit Google’s account chooser help doc for complete instructions.
Found via Lifehacker.