Quadrature rules
The online encylopedia of quadrature rules is a reference website that lists a number of quadrature rules.
Quadrature rules are sets of points and weights that are used to approximate integrals. If ${p_0,\dots,p_{n-1}}\subset\mathbb{R}^d$ and ${w_0,\dots,w_{n-1}}\subset\mathbb{R}$ are the points and weights (repectively) of the quadrature rule for a single integral, then:
$$\int f(x),\mathrm{d}x \approx \sum_{i=0}^{n-1}f(p_i)w_i$$
Libraries
All of the quadrature rules included in the online encylopedia of quadrature rules are included in the quadraturerules library, which is available in the following languages