Fluxify is a great Silverlight app that will resize your image and then email it to your favourite recipient. This is the only client size resize app that I can think of that can resize an image without first uploading and that doesn't require you to install it or assign special permissions.
Great news for those keen on Silverlight and FJCore, they have recently posted the source code to the FJCore library. All that is needed now is some crop functionality and you have a great little uploader app for any CMS.
It appears the Fluxify app is no longer available from the original website and the FJCore source submitted to Google Code.