Disclaimer: I'm about to promote my own company, Surround Technologies[1]
Reading through all of the comments so far, I'm seeing solutions that give you a CRUD web app... and nothing else. If that's all you really need, then that's fine. For the past seven years I've been working with large companies who need Enterprise-class CRUD apps, with Enterprise-class requirements that go far beyond what you get out of the box with most of the cobble-it-together-yourself solutions being mentioned here.
Surround Accelerator is a CRUD Application Generator and Framework. To use it, you first develop an optional plugin that customizes the generator, then you run the generator and point it at your database. It loads the schema, does a bunch of analysis, and asks you a bunch of questions. Your plugin is used to govern the analysis and provide standard answers to the questions, so that you can customize the result consistently. Finally, a set of C# web services and applications are created. We're currently producing both a WPF desktop application and a fully-responsive ASP.Net MVC SPAs. Both GUIs are highly customizable; our framework is very flexible and all of the code you need to change to customize the application is part of the generation rather than locked up in the framework.
Generation isn't a one-time thing though; if your schema changes we've got tools that you can use to re-generate just the parts you've changed, or to add generation for the parts that are new. Typically, the way we've structured our code to allow for customization, it's easy to merge your customizations back into the generated code.
If any of this interests you, please visit our website. We've got a number of videos showing the process, a bunch of demos, and many case studies and testimonials from actual customers.
[1] http://surroundtech.com/