Troy Wolbrink's TNT Unicode Components are essential if you are doing Win32 Delphi development but need to support Unicode. The components are designed so that they can easily be substituted for the matching VCL components. (TNT Unicode is now TMS Unicode)
JEDI Visual Component Library - The JEDI Visual Component Library (JVCL) consists of a large collection (currently ca 500) visual and non-visual components which can be instantly reused in your Delphi, Kylix and C++ Builder projects.
Mike Lischke'sVirtual Treeview component suite. Virtual Treeview is a very flexible treeview control. The control uses a "virtual node" paradigm to achieve impressive run-time performance. Basically, initialisation is divided into 2 stages: (1) Fast pre-initialization; and (2) Formal (and possibly expensive) initialization. The virtual paradigm defers formal initialization until absolutely needed for display purposes. See the Virtual TreeView subsection on this wiki: VT Home
Delphi Central provides various free Delphi components all come with full source code and also include C++ Builder equivalent code. These components are written more with learning in mind but can also be used in your own programs.
Components for Purchase[]
Encephalon EvilOgre Open up your applications to a stunning world of 3D data navigation. Easily navigate complicated data relationships in a 3D web that the user can spin to look at from every angle. Navigation is as simple as clicking where you want to go.