Programming Stuff
Well, at the moment this section of the site mainly contains source code and stuff to download, but I may get round to writing some tutorials here someday...
Note that the source code (with project files for MSVC v6 and Apple Project Builder/XCode) is also available for some of the more recent plugins - see the plugins' individual pages, or the actual plugins page.
Tutorials
Setting up XCode to Build a VST Plugin - Simple walkthrough of the steps required to build a VST plugin on OSX with XCode v1.5.
Plugin Editor Stuff
VSTGL - An interface to let you use opengl for your plugin editor (used in Harmonical and Simple Colour Organ).
MultiGUI - An interface to let you use more than one editor window for your plugin (this is mainly so that you can mix a standard 2d editor with a VSTGL one, also used in Harmonical).
Downloads
Polyphonic Synth Tutorial Code - An example project demonstrating how to design a polyphonic synth using the VST standard. Presents 16 voices of a simple enveloped sine wave. Projects included for MSVC v6 on Windows, and XCode (v1.5) on OS X.
Simple Controls - An incomplete set (14 out of a planned 22) of VSTGUI widgets designed so that you don't need to use any bitmaps in your gui. I did mean to add a lot more widgets to this collection, but to be honest I ran out of steam on the project. As it is, these are meant for use with VSTGUI v2.3 (? - the one included with Steinberg's SDK). They cover quite a few bases (bitmap-less frame, gauge-type slider, keyboard display/slider, etc.), but you can see the original list of widgets in Simple Controls.txt (in the zip file). Most of these widgets are used in one way or another in the ndcMIDI pack.
Niall's Pedal Board - A simple VST host for Windows, written using the JUCE library. It's kind of esoteric, and to use it properly you need to get out your soldering iron and build a joystick-interface-based hardware controller for it, but it seems to work quite well for what it does. The source code's included, and there's screenshots here.
VSTGUI Builder - A RAD-style tool to construct VSTGUI interfaces, and generate the corresponding source code. There's a screenshot here (scroll down).