Support for oEmbed, which was added to WordPress in version 2.9, is very nice. Unfortunately the generated oEmbed code is not easy to be centered in the text, which is a common request. This plug-in allows for centering (or even other styling), although it will not solve it by itself, just makes it possible.

This plugin wraps all oEmbed code into div tags with several classes set:

oembed
oembed-mediatype (e.g. oembed-video)
oembed-server (e.g. oembed-youtube-com)
oembed-mediatype-server (e.g. oembed-video-youtube-com)

Then you can specify in your theme CSS (in the file style.css) the way you want the embeds to behave. E.g. by adding the following code to style.css:

.oembed {
  text-align: center;
}

you will make all oembeds (videos and pictures) to be centered; anyway, if you understand CSS, you are not limited by centering, but you can add much more (like frames around pictures etc.)

License

WTFPL License 2.0 applies

           DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                   Version 2, December 2004

Copyright (C) 2004 Sam Hocevar <[email protected]>

Everyone is permitted to copy and distribute verbatim or modified
copies of this license document, and changing it is allowed as long
as the name is changed.

           DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
  TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

 0. You just DO WHAT THE FUCK YOU WANT TO.

oEmbed styling

License