This article shows examples of how to embed video and other iframes in a responsive web design and has examples with YouTube, Vimeo and Slideshare.
I found a neat little CSS trick on the A List Apart article “Creating Intrinsic Ratios for Video” and I did some experimenting with it. (Yes, I had to look up the word Intrinsic…)
The problem with embed code that you copy from websites like YouTube is that they often contain a fixed width and height in pixels. And that does not work too well in responsive designs. In a responsive design we have a container with a relative width and we want the embedded object to be relative to our container. This is not possible with all embeds as some of them insist on having a fixed width. If you encounter such embeds, the workaround is probably to move some of the code to the server side or javascript and set the width to the pixel value that you think is most appropriate. It will work, but it will not be flexible like the method shown here.
This technique is fully flexible and I have tests below with Vimeo, SlideShare and YouTube (sorry if this post took long to load…). Here are the steps to make it work.

A List Apart om hur man bäddar in flash-filmer på ett sätt som fungerar med webbstandarder.

En guide från Apple för hur man bäst bäddar in quicktime-filmer på webben.

En samling info om hur att använda quicktime på webben.

Hur man gör fullscreen av en quicktimefilm från en länk med både qtl och även javascript.