I'm not saying it's not needed, but there's a huge chunk of the C++ world that doesn't do web development. The other things I mentioned are more generally useful. In particular, XML support probably needs to come before HTTP support.
Not that I'd turn my nose up at standard HTTP support.
I recommend the libraries from CodeSynthesis for your XML and database needs. The documentation for both is superb, and the APIs are crisp and modern. JSON I'd go with either JSON Spirit (boost header dependency) or JsonCpp (git version[0], since there hasn't been a release in 3 and a half years. 1.0 was tagged recently though)
For webdev I've personally used CppCMS, which is of good quality, although it is a framework and not a toolkit (it's MVC and the views want to use inheritance, has its own networking and template framework etc)
I know there are libraries out there; I was talking about getting more things standardized so programs can mix and match these libraries with fewer translation layers. For example, boost spirit is a bit out there for most projects.
Not that I'd turn my nose up at standard HTTP support.