Easiest way I found was:
www.tinypic.com
Use their browser to find your photo and click open. (The file box should show the URL). Click on resize to message board. Click upload.
When the URL comes up, right click on the one for message boards/forums, click copy, go to the body of you post, click on it, then right click and then click paste.
The URL should appear. (Preview your post - the picture should appear).
I know it's a lot of clicks, but I tried photobucket and a couple others, and they are even more confusing. I'm not real saavy with this stuff, and it was fairly simple for me, once I got the hang of it.
And with Tinypic, you don't need an account unless you want to organize your photos there. It's free to sign up.
Good luck.