Tip: Resizing and Manipulating Images for the Web
Often, images you'd like to use aren't the proper size, and as you know, our tools and systems do not resize images. It's important to resize images before you upload them. Recommended image sizes (in pixels) are listed in each of the toolsets.

Follow these links for free image editors that you can use to resize graphics:

• IrfanView
• FreeSerifSoftware - PhotoPlus 5.5 and other free downloadable image editing software
• GIFWorks! - online gif image editor
• myImager - another online image editor

A good tutorial @ Webmonkey