I recently had a need to re-size the content of iFrames for a site that uses iFrame for various reasons.
This is not an original work but a collection of demos and sample code.
1. jQuery Sample: Jscheuer1 at Dynamic
Drive has the most usable example (IMO). Use the links below for the online demo and to download the code.
2. iFrame content on other domains:
In order to re-size iFrames the iFrame content page you are rending needs to be on the same domain, or you have to have some control over the page that contains the iFrame content. In the case where the page is not on the same domain, but you own the code this link at CSS-TRICKS
goes into how to set this up.
Great article on how to upload and crop images at Mikesdotnetting blog.