Picasa (click to download) is a free photo program from Google that will search your computer and organize your photos. You can then do simple edits such as crop, enhance, rotate, and many others. Then you have them in your own albums on your computer and can upload selected images to free web albums for storage. You can determine the size of the images you load up to an album. Once they are in a web album and you can link them in forum posts.

The photo above works as thumbnail size and was copied from the smaller photos in Picasa.
This larger image was copied in using Picasa's right click menu item "copy image location" while hovering over the full sized web album image and then pasting this between the image brackets in the message edit window. This image is 800x600 which works well for most of our viewers. You can resize the image if you want by editing the image tag information at the start of the link.

Here's another that should work well for posting sizes.

Final test...
Set the center button, then image button and pasted in "image location" from the web album.

Try this, especially if you don't already have a good easy-to-use image organizer & photo editing software. The price is right (free), it is constantly being upgraded, and the online storage is also free - so it may totally replace a Photobucket account for many folks. It is one stop shopping making it easy to do everything from downloading images from you cameras USB port, to editing, uploading to the web, and then posting the images in messages here. Later you can learn how to do things like Ken Burns slideshows and such all with the on-line images in your albums.