I found SCons, which looks useful, but it's not exactly what I'm looking for. I don't really want a build tool; what I really want is a package manager.
Other languages have similar tools:
I would like to have a single database of open-source D projects that can be integrated into a larger application with only a couple commands, such as (assuming dpack is the command):
# get source from database, run build script if there is one
dpack install some_package
# builds current package, grabbing dependencies as necessary
dpack build
# removes source (build will fail without it)
dpack remove
Is there anything like this for D? If not, I'll probably end up writing it myself.
Update: Please see the top rated answer about Dub. It is now the defacto package manager for D and will soon to be the official package manager which will be included with D compilers.
There have been several attempts by various people and a lot of discussion. The only one I know of that is actively being worked on is Orbit by Jacob Carlborg.