I keep anywhere from $15 to $200 in my checking. It earns me nothing, so I keep the minimum in there. Its basically a flow-through account to other things.
I keep $250-$1k* in a traditional (US) savings account. It earns very little, but its better than the checking account, and I can transfer the funds to my checking account in about 30 seconds in a pinch. I keep the money here as an "I effed up the math in my checkbook" buffer, emergency funds, etc.
The rest of the emergency funds are kept in online savings accounts and CDs. Much better interest rates, but a pain in the arse to get to in a hurry.
*To keep the account free, I have a monthly deposit of $10 auto deposited. Once the balance reaches $1k I pull out $750 to invest, and start all over again with $250.