Grid system for user interface
I hope someone will be helped this list. Tried to collect the most interesting systems.

Bootstrap Grid System
The most popular option for us. More often 12 columns with indents. Standard and simple system. Most of the interface market is built on these principles, and many of the below listed systems are created on this basis. Very quickly learn, but this grid creates an internal standardization.
Although most likely this similarity will be see only designers.

Material Responsive Grid
Google material design. Most designers have come across this system, it is very convenient in its essence, the guides are well described. One of the most advanced solutions on the market. But unfortunately obliges to use the systems that Google offers, but does not stop changing them ;)

Flexbox Grid

Custom modular grid based HTML
There are many examples when taking the bootstrap base principles. It’s a 6 or 12-column system and designers much rework it. Change the size of individual blocks, make them unequal, and so on. It’s a trend now.

Crow Grid Framework
Not very popular in comparison with other system, reminded grid constructivist posters, interesting and fresh. Maybe once it becomes very popular.
Developer twitter: kortekim
Human Interface Guidelines

Apple. Very little said about modular systems, but principles so intersting. Suitable of course, first for iOS.
Human Inter
www.behance.net/gallery/45462945/Human-Inter

A rather peculiar system, which is not suitable for every project. The principle is based on the golden section and the Vitruvian man. When used, one of the most important aspects is the horizontal line. Grid, which based on bootstrap.
If you want to see rules and guidelines, write to me on email: ivantsanko11@gmail.com
Developer twitter: ivantsankoart
Karl Gerstner: Designing Programmes
A very interesting system, at the moment it is difficult to apply it to modern interfaces. I was interested reading about this system how it works and what principles. If you have desire, it’s could be very interesting realize in the modern web.

Fluent Design System
Absolutely new system from Microsoft. Today it is little known, but the presentation video very interestingly shows how they represent modern design.
In conclusion, I want to say
I was happy to help you find new systems and talk about them.
Social networks
Twitter: https://twitter.com/ivantsankoart
Behance: https://www.behance.net/tsankoi2f09
Email: tsankoivan11@gmail.com