jwenl

This plugin provides support for using oEmbed in your WordPress blog.
Rick media Example: 
[oembed:http://polldaddy.com/oembed?url=http://answers.polldaddy.com/poll/2431815/&format=xml] 
This will put the selected polldady poll on your blog
Photo example Flickr: 
[oembed:http://www.flickr.com/services/oembed/?url=http://www.flickr.com/photos/23886028@N04/3983995799/in/set-72157622398187791/] 
This will put a Flickr photo into your posting.
Video example Youtube: 
[oembed:http://www.youtube.com/oembed?url=http://www.youtube.com/watch?v=yvdbqcbRH50&format=json]

oEmbedder

This plugin provides support for using oEmbed in your Wordpress blog.

Konstantin Kovshenin

Twitter Embed requires no configuration, it works out of the box right after activation. Copy a link to a tweet on Twitter.com and paste it on a line by itself in your post or page editor. When viewing the post, you’ll see that the link has been replaced with the embedded tweet with options to reply, retweet, favorite and follow.
The plugin uses Twitter’s original widgets API, the shortcode and embed HTML are available too. Embed HTML is reversed to a Tweet shortcode when HTML is filtered (for authors or contributors). The tweets themselves are cached in post meta for better performance.

Twitter Embed

Easily embed tweets in your posts and pages by posting the tweet URL on a line by itself or by using a shortcode provided by the Twitter interface.

oEmbedder vs Twitter Embed