I use Imageshack, works very well for me
http://imageshack.us/
If you click Browse and choose the pic you want to upload, then where is says 'resize image?' you can click on the dropdown menu to pick a suitable size. I use 640x480. Then once it has uploaded it will provide you with a lists of links which you can use - I use the one right at the end, should end with jpeg.
Or you can use photobucket but dunno how that works
HTH
