An interesting article from BBC News with content from David Haye (former world heavyweight champ) and Rob McCraken (former champion boxer and head coach of the British Olympic boxing team).
Includes sections on:
1. The quest for perfection
2. Speed kills
3. Breaking down a knockout
4. Boxing basics: First steps to a perfect punch
5. What it feels like to be knocked out
Its interesting, with cool web tech to analyse pro fights frame by frame, but no surprises.
Speed, timing, and taking position, getting as much of the body weight into the punch as possible.