Cook is a great piece of kit for creating Joomla components (and also modules and plug-ins in the future). It uses a drag-n-drop interface to build tables and fully featured pages. You can test your component in a sandbox before downloading it packaged up ready to install. It is still early days and there are a few gremlins but the developer is responsive on the support forum. It is a commercial product but currently you are given 200 points to get you started and points are deducted based on the ammount of dragging and dropping done. More points can then be purchased after that or a block of time can be purchased.