Are you actually trying to place an image or a whole div within the paragraph?
Either way your solution's floating the image or div.
If you try floating a div within a paragraph it won't validate though (not too sure why as they're both block level elements). If it's an image then you've got no problems- just float it right and give it some margins or padding to hold the text away a bit and you're fine.
To float a div I'd put it just before the paragraph and float it. That way it will sit over on the right hand side level with the top of the paragraph and the paragraph text will flow down around it.
Image version with inline CSS just for here - obviously move the CSS to an external stylesheet though!
<p><img src="images/yourimage.jpg" height="100" width="100" alt="your image" style="float:right; margin:5px 0 5px 5px;" />Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Vestibulum ac leo vel dolor tempus interdum. In hac habitasse platea dictumst. Quisque ligula sapien, auctor vel, nonummy a, ultrices a, justo. Ut pretium viverra neque. Nulla rhoncus tincidunt dui. Aliquam eu massa vitae dui imperdiet aliquet.</p>
Div version:
<div style="float:right; margin:5px 0 5px 5px;width:100px; height:100px;">Hello, this div is floating!</div>
<p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Vestibulum ac leo vel dolor tempus interdum. In hac habitasse platea dictumst. Quisque ligula sapien, auctor vel, nonummy a, ultrices a, justo. Ut pretium viverra neque. Nulla rhoncus tincidunt dui. Aliquam eu massa vitae dui imperdiet aliquet.</p>
Edit: doh - Roger got in before me!