Multimedia
obviously a draft, but there's no such page and users seem to expect it.
Playing multimedia
The Browse web browser activity can play video and audio links (using the Totem plugin).
Supported formats
To see what formats Browse supports, type about:plugins in its location field and press the enter key. (If you don't see its location field, click its "Browse" menu.)
The primary open unrestricted file format for audio and video files is [OGG]. So if you see a link to a .ogg file, your XO can probably play it. This is a "container" format for many different ways of compressing files. The standard OLPC system software can understand some but not all of these.
What happens with an unsupported codec in a .ogg file?? - need link
What about MP3 files?
Note that the standard OLPC software does not support common-but-restricted media file formats such as .mp3. See Restricted Formats for an explanation why.
However, it (should) be easy to add support for these, at the risk of violating software patents.
Test
Need a link to good sample files
Maybe Data file formats should have a link to a sample of each kind.
Getting multimedia
There are collections that have audio and video files that you can download to your laptop.