chuck85:
I'm using a Mac so there is no right click!
CTRL + Click then, or if your on a macbook/pro two fingers on the mouse pad + click.
….anyways for Flickr:
1) Go to your photostream for example: http://www.flickr.com/photos/46004836@N02/
2) Click the picture you want, say for example 'Snow by Carn Kenidjack'
3) Click the 'all sizes' button just above the top left of the pic.
4) Once you have picked the size you want, for this example i selected the 'large' image, right click the picture and select 'copy image address'.
5) Go on to STW click the IMG button above the text box you are writing your reply in and right click and paste and you should have something like this : http://farm3.static.flickr.com/2780/4259558884_b8a64ae943_b.jpg. Hit ok and your done.