Latenite is a Z80 IDE designed primarily around TI-83 Plus and Sega Master System development. It has been designed to be completely extendable - you can add new project templates, assemblers/linkers, help files, tools and they'll all be able to talk to the IDE.
One complication of using Latenite over, say, Notepad is having to get used to the way Latenite manages projects. I have provided a guide to getting started that takes you through setting up a project, editing the source and compiling to binaries - which should cover the basics.
I have documented all the various parts of the IDE that can be customised. Use the navigation bar on the left hand side of the screen to view more information.