To wrap text around a youtube (or other) video in WordPress, switch to the HTML view:
Paste in this code before the video embed code:
<div style="float:left;margin:0 10px 5px 0;">
(click here to see the youtube embed code)
Paste in this code after the video embed code:
You will get these results:
This is an example of wrapping text around a youtube video. First find the video on youtube, then start your blog post. Then copy this code
<div style="float:left;margin:0 10px 5px 0;"> and paste it into your blog post while in HTML view. Then get the youtube embed code and paste it in next. Follow that with the code </div>. You can tweek the code if you want it to float on the right or left and the padding around by changing the code.