I have been playing around with the new cfimage tag in coldfusion 8. I am very impressed with the resize capability. Coldfusion 8 seemed to do a great job resizing my images into thumbnails. I created a tutorial here.
Here is a little bit of code to create thumbnails.
<cfimage action=“info” structname=“imagetemp” source=“Path to your image”>
<cfset x=min(150/imagetemp.width, 113/imagetemp.height)>
<cfset newwidth = x*imagetemp.width>
<cfset newheight = x*imagetemp.height>
<cfimage action=“resize” source=“#Path to your image#” width=“#newwidth#” height=“#newheight#” destination=“#thumbnail destination#”>
Update: My Using CFIMAGE to Generate Thumbnails tutorial was published at learncf.com

Hi Damon -
I just started playing with this, too, and I am both impressed (at quality and speed) and relieved (at no longer jumping through extraneous hoops for images!).
I put up a little upload-resizer demo here
http://mredesign.com/demos/cfimage-example/
(no tutorial, though)
@Damon:
You might want to look into the imageScaleToFit() function. The "resize" option doesn’t keep proportion, where the imageScaleToFit() function does.
I really like what you put together on your demo. Do you have the code for download? This demo could come in handy! Thanks, Robin.
Yes you can download the code at http://learncf.com/zip/19
don't forget to round your new values
It's bogging down my site, I think–anyone else experiencing delays with more than a few images on a page??
Yep the performance on concurrency would probably bog down your server . If I use a 1.3 MB jpg to resize.
It takes about 13 seconds after the upload is complete to resize.