Another
for Postimages.
In the menu that is displayed when you click on 'Do not resize my image' I personally find that 320 x 240 gives a nice small one for inconsequential images while 640 x 480 shows a decent sized one for proudly displaying your efforts on the forum.
After you have selected your image, you copy the Direct Link on the second line down by clicking on the blue-and-white icon at the righthand end of that line. That automatically copies the link to your clipboard, and then you click on the 'Insert Link' button above the message you are composing on the forum, it's the one directly below the B for Bold, and paste the link. Job done!