The invaluable Null Hypothesis: The Journal of Unlikely Science reproduces an amusing article about research done for British Gas in 2004 into Sod's Law. On this side of the pond, Sod's Law is more generally known as "Murphy's Law." The research found:
…based on over 1,000 people's experiences, that the original Sod's Law—'anything that can go wrong, will go wrong'—is only half the story. It can now be improved by the use of a new rule—'Things don't just go wrong, they do so at the most annoying moment'.
This explains why your email will most likely crash as you try to send something important, how the chances of your spilling a drink down your clothes are highest just before a date, and why it's a safe bet that your heating will most often break down during a cold snap.
Previous studies have shown that Sod's Law isn't a myth—toast will fall butter-side down, odd socks do breed and string can tie itself in knots. Our formula now allows people to calculate the chances of Sod's Law striking, and thus try to beat it.
Check out their formula here. Some other corollaries are:
HOWE'S LAW. Every man has a scheme which will not work.
ZYMURGY'S FIRST LAW OF EVOLVING SYSTEM DYNAMICS. Once you open a can of worms, the only way to re-can them is to use a larger can.
SKINNER'S CONSTANT. The quantity which must be multiplied by, divided by, added to or subtracted from the answer you get to give the answer you should have got.
LAW OF SELECTIVE GRAVITY. An object will fall so as to do the most damage.
A list of other Sod's Law *corollaries to Sod's Law is available here.
*A Sod's Law attack during editing.