I use http://tinypic.com/index.php
and resize with their easy field prompt offering
i use 15" screen from the drop down RESIZE BOX
after I have downloaded the file from my computer using the that sites BROWSE button
once it is downloaded I select and copy what under the IMAGE CODE FOR FORUMS AND MESSAGE BOARDS
and then paste in your post field here..it is really easy. the only drawback is the answering the sites question, which is their way of getting paid advertising... so you can use it for free.
if you have a lot of pictures, then you should use a resize feature on your computer. i bet almost every computer comes with a photo editor!!! but when you resize , do not just save!! NOTE: you must find out here what the max size is, so you can resize down below that ...it could be in pixtels, or it could be in KBs
use SAVE AS and rename the picture...i usually call it the same name as before but ad -sized. that way you still have the original sized picture on your computer
once you do it, youl realize how easy it is.