If your blog has the WordPress Video Plugin activated, it’s easy. Put the name of the provider (youtube, flickr, dailymotion) into a set of square brackets, along with the provider’s video source ID (the part that’s in bold here: http://www.youtube.com/watch?v=aWYmVJqV7ac), and you’re all set.
for example: [youtube aWYmVJqV7ac]
The list of providers supported also has detailed examples.
If you’d like to use this on your blog, just let us know.