Yeah. I have been using Photobucket since "Day-1" for image posting on every forum site I use. I always maintain complete control of the pictures that way and they're never "uploaded" to the site I post to.
The post link looks like the following (MINUS the "hash-tags"):
[#IMG]http://i14.photobucket.com/albums/a317/nixypixy07/flange_zps735c634a.gif[/IMG#]
Like
jbcurt00 said, all you do is (right-click) copy the link (from the hosting site) and paste it into your message text as you type.
You can also do the same basic thing in any normal email sent to someone. The advantage of sending someone a link (in an email) is you don't actually send the file in the body of the email which keeps the file size much smaller.
It was more of a problem when people had slow dialup connections. Trying to open an email with a HUGE file attached made it look like the connection failed while it was downloading the attachment! If you made the attachment a file "link" then the recipient didn't download the attachment until they actually "clicked" on it. (THEN it took for ever!!!)
It's still a problem (less of though) with the really slower DSL connections.