A Web 2.0 Application Builder

In the last few months, I've been thinking of something like this, but here it is: NING, a Web 2.0 application builder.

I've not tried it but it looks like a large number of others have. "[Ning] allows users to mix and match tools and build their application, the costs fall to zero since Ning hosts the site for nothing. It has about 17,500 applications running on it," says a Financial Times report.