Pecha Kucha was started in Tokyo, Japan in February 2003 by Astrid Klein and Mark Dytham as a designers' show and tell event to attract more people to SuperDeluxe, their multi-media experimental event space they had set up in Roppongi.
The idea behind Pecha Kucha is to keep presentations concise, the interest level up and to have many presenters sharing their ideas within the course of one night. Therefore the 20x20 Pecha Kucha format was created: each presenter is allowed a slideshow of 20 images, each shown for 20 seconds each. This results in a total presentation time of 6 minutes 40 seconds on a stage before the next presenter is up. Each event usually has 14 presenters. Presenters (and much of the audience) are usually from the design, architecture, photography, art and creative fields, but recently it has also streched over to the business world.
Since then the concept has spread. If you visit Pecha Kucha.org you can see the listings for "Pecha Kucha Nights" being held in cities all over the world.
Here is an example of a Pecha Kucka presentation I found on YouTube on the subject of "Emotionally intelligent signage".
Another excellent resource and favorite site of mine is Presentation Zen.
The post comparing the presentations of Steve Jobs and Bill Gates are a classic: Gates, Jobs, & the Zen aesthetic