If a pipe is going to leak, you can be sure it will happen on a weekend or holiday when you can't reach a plumber. So, the following may by helpful in controlling the situation until the plumber arrives.
If the leak is in a main pipe - not a leaking faucet where the water can be turned off at a valve underneath the sink - then the main water should be shut off. Not only will this reduce the pressure at the leak but also allow repairs to be made more easily.
Before attempting any repair make sure the pipe area to be repaired is dry, otherwise the products used for the 'fix' may not hold. Also, if at all possible, drain the damaged pipe if unfrozen. If frozen, make repairs on the frozen pipe.
If the damaged area is on a drain pipe or trap, there will be no pressure or water unless the faucet is in use.
Standard fixes for small leaks are:
Plumber's Epoxy - two putty-like materials that are kneaded together to a uniform color, then applied to the leak. This can be used on a puncture or for leaks that appear at a threaded joint.
Mighty Tape - a plastic tape that can be stretched and wound tightly over leaks (we used this several times and it works really well) Punctures and joints of pipes (inside or outside)
Plug - A pencil point works for tiny leaks by jamming the point into the hole and breaking off the lead tip. Afterwards, the plug can be secured with any plastic tape wrapping the pipe 2-3 inches to either side of the plug.
Standard fixes for larger leaks:
Hose Patch - temporary patch made from section of rubber hose. The hose piece is slit lengthways and placed around the leak. It is then secured in place by using several pieces of wire wrapped around the pipe and twisted to make tight, or metal hose clamps. At least 3 clamps should be used to secure the hose.
Semi-Permanent (Pipe Sleeve) - When repairs need to be postponed, a pipe sleeve can be used for a length of time. These can be used at first or to replace any one of the above temporary fixes. They come in different sizes and diameters so be sure to get the right size.