I set up a "Rainy Day Fund" by way of a savings account with my primary bank. I have it set to transfer a small, specified amount from my checking account to my savings account on the same day I get paid via direct deposit. Basically, it tends to itself and grows a bit every couple of weeks. And if I need the funds for that "rainy day"…be it sudden car repairs, extra vacation funds or a sudden GAS-attack…I can instantly transfer it to my checking account with a single phone call.