I just use
http://photobucket.com/
Sign up and just start uploading. When done you will get 3 different choices of code to use. For this forum I use "URL LINK", hit that button and it will be copied(cache), back in your "reply to thread" window hit the icon that looks like a "mountain with a sun" (insert image) and paste that URL and away you go!
You might know this but...there it is :p