Microsoft Popfly is based on their Silverlight software (their version of flash).

The alpha release has a drag-and-drop mashup creator that is really amazing. Elements of the mashups are called ‘blocks’, and you can drag blocks onto the desktop and connect them. Information items are selected from drop-down menus – no programming language required. One of the drawbacks at this early stage is that they don’t play nicely with existing flash files, so some of the potential mashups give an error message (example – library book photos do not display). There are currently more than 250 blocks (data sources) to ‘mash’ with, so that’s quite a nice little sandbox for developers.