The Sidekick does have a USB port but it is for developers only.
I would suggest that you email the pics to yourself (from your sidekick) or just save them to your computer from your desktop interface through T-Mobile. My guess is that you already know how to get your pics from the sidekick though.
One way to get images onto the forum is to register on a free image hosting website such as cardomain.com, then simply add the image on your post. When you select to add the image it will ask you for the URL. Put in the URL of your pic and then it will appear in your post - even though it is through an external link.
that is one way...