Well I use ImageShack as I read the terms and they didn't say I couldn't link the pictures in forums (some will say not to direct link as it takes up bandwidth). At the time I didn't need to sign up but I did so I could have a gallery to manage my images. Not sure if its still no sign up required.

http://imageshack.us/

When I upload an image, just like searching and adding a photo to an email, I get a number of options for code that works with forums.

Opps, sorry I cut off the end part of the link. The full link is

Here's a very old thread that I saved. It is based on posting clickable links, but also has instructions for inserting photos directly into posts.

Here is a link that might be useful: clicky