There are lots of times a tripod comes in handy. Of course you might not have one on hand when you need it most. Here are three of my favorite techniques to overcome the lack of a tripod.
Swaddle the Camera
This technique works best for time-lapse. Take a sweatshirt or jacket and ball it into a nest of sorts. The camera literally sits inside the nest which absorbs vibration and keeps the body from falling over.
Find a Bar
This technique is best for HDR or low-light shooting. Find a railing, a park bench, a garbage can even. The key is to press down on the camera so it stays stable. Ill take advantage of a continuos shooting mode and auto-bracketing so the camera can quickly fire all exposures.
Find a Pole
This is another variation on the theme above. The challenge here is often that the surfaces are rounded. Ill often try to pad the bottom of the camera with a jacket or a hand. Ill often use the camera strap and wrap it around the pole (just keep it under tension to further stabilize).
Disclaimer: These are just a few ways to solve the lack of a tripod.