The other day someone was asking a question on the WinForms forums about the PropertyGrid class. This control is what you typically interact with to set properties in Visual Studio, and it's a very handy class that you can use at runtime as well for a quick way to allow users to edit an object. It is based on WinForms, however, and that got me thinking about what's available on other presentation stacks.
For Silverlight, the Silverlight toolkit provides the DataForm control with similar capabilities.
For WPF, it appears that various projects have done ports of one or the other. A good starting point is to simply do a search for either on http://www.codeplex.com/ and see what's available.
Is there anything obvious missing here? WPF makes it so easy to craft a specific template with data binding that I would imagine that in most cases it's not too time-consuming to craft a one-off data template for your types that will offer a more specialized user interface.