From NSIS Wiki
This is the place where NSIS users can find and share script code, examples, plug-ins, tutorials, software, graphics and everything else that's related to NSIS. Any user can add or update information. The sandbox can be used for editing experiments.
Examples of how to implement installer actions.
Applications to edit and compile NSIS scripts is a convient way, with features like syntax highlighting, code folding and outlide view. Most development environments also include a dialog designer to create custom pages.
Functions & Macros
Functions usually perform one specific task, like comparing a version number or searching for a text.
Graphics and UIs
Icons, wizard and header images and complete custom wizard interfaces.
NSIS Help & FAQ
Additional NSIS help including a list of frequently asked questions (FAQ).
Plug-ins add new features that can be called from NSIS scripts, such as file downloading, XML file parsing and a lot more.
Real World Installers
Examples of complete installers that have been used to distribute real applications.
NSIS-related software like script generators and converters.
Step-by-step guides that explain NSIS features.
List of all Pages in the Developer Center