A collection of ...
To provide a place where people who are looking for speaking opportunities and people who would like to attend events can easily find what they are looking for.
To make it easy for people who cannot attend events to find and watch presentations from previous events.
To make it easy for Open Source and Tech conference organizers to list their events (it is just a pull-request).
The site seriously needs some design and more data. You can contribute events, and corrections to existing data. One of the most valuable contribution might be to add "topics" to the events and "tags" to the videos.
If you'd like to see additional podcasts listed here, file a ticket or open a pull request.
There are plenty of places where events are collected. Some are generic places where any type of event can be listed. Other are for a specific technology or a specific country.