To make life easier as a D developer many projects have been started, and a few matured, just for this purpose. Categories with many options have their own page, otherwise a link to the project page is provided with a small discription.
(in alphabetical order)
Pluggable demanggler for D written in C.
Dimple, or "D import-list explorer", extracts import declarations from D source files and builds a dependency graph for visualization.
Exuberant Ctags can be patched to collect tags from D source files.
Cscope is a more powerfull alternative to Ctags, but they can both be used at the same time.
Source Code Beautifier for C, C++, C#, D, Java, and Pawn