2D/3D Design & Modeling

Mesh Drag-and-Drop Demo (C++ source only)

Mesh Clone Brush Demo (C++ source only)

Mesh Segmetation Tool (C++ source only)

libgeometry: a discrete shape modeling library (C++ source only)

Pencil: A Simple Sketchbook (C# source only)

As-Rigid-As-Possible 2D Shape Manipulation Demo (binary & C# source)

2D Laplacian Curve Deformation Demo (C# source)

Implicit Surface Mesher (C++ source only)

2D Blobs Demo (C# source only)

Surface Parameterization

Discrete Exponential Map Demo (binary & C++ source)

Geometry Processing

Matlab Mesh Toolkit (matlab source)

Miscellany

Sketch UI Framework (source-ish)

Shapeways.com API wrapper (source)

Generic Solver Interface (GSI) (C++source)