You could try Picasa2, a free utility available from Google. This gives you a one click way to re-size for emailing. You have a certain amount of control over the resolution from the pictures "properties".
Another way is to save the file to by document or my picture in windows XP. Highlight it, right click and select picture resize from the drop down box. You can then make it as small as you like. That is provided you are using XP