Code for posting "in post" videos has been added to the forum. It's really simple to use. Just a bit above the posting window, when you are posting a topic or a reply, you will notice a row with video buttons. You can let the mouse hover the buttons to check what video type is associated with each button. Click the button that corresponds to the type of video you want displayed. A couple tags will be shown and you can then post the link to the video inside the tags.
As an example, the code for a YouTube video will look like this: