flexonrails.net has an example of a Flex and Rails image converter that uses Rmagick to convert images into numerous file formats (jpg, png, bmp, gif, pdf, eps). You can upload multiple files, convert them, and then download the converted files in a zip file, there’s also a progress bar for the upload and download progress.

I like that it doesn’t look like a ’stock’ flex app. Flex can use style sheets to quickly change the appearance of any component including buttons, combo boxes (drop downs), and the various containers (Flex divs). This let’s you customize your app with creating any graphics and is a big time saver if you want every part of your app to have a certain look or carry the clients branding throughout the app (and it’s guaranteed to look the same in every browser!)

Adobe has an example of Flex Style Explorer which shows all the styles that can be configured.