Some people that are new to forus always ask me "How can I upload pictures to a post?" , well as everyone knows you need an external hoster, what an external hoster does is uploads your image to a server and gives you a link, that link takes you directly to you image. Now after you get link, you have to use the BBCode which is found at the top of you New Topic or Reply page, all you do is click the IMG code at the top, and put the link between the [IMG] link [/IMG] and it will show up in your post. But also important for Forums is Thumbails, thumbails are a form of image posting that (in you post) appear as a small image, then that images is hyperlinked to the page, when you click the image it takes you to the page where you can see the image full size.
File Hive- Its great for people who dont upload that much, but its great cause this Hoster saves your last 5 uploaded images.
Photo Bucket- Great hoster, you can edit images online, you get HTML, BBCode in the upload, but this hoster has the nasty habbit of getting rid of their old images, so I do not recomend this to people who upload alot.
Image Shack- This uploader is great because its a BETA hoster, meaning you do not have to register, but being BETA also has a downside, you do loose all you previous uploaded images.
Image Hosting-PLUS- This is a great uploader, you can upload multiple pictures at the same time, you get them saved, and you get 20MB of space for upload, if you would like more please visit the support forums for more information on how the How To's