The modules for the International Space Station come from 16 nations, the US and Russia are the main players. The other partners are Canada, Japan and the European Space Agency (ESA), which itself is made up of eleven countries. Brazil will provide a series of smaller hardware items.
The main parts of the ISS are
Functional Cargo Block
The first part of the ISS, launched by Russia in Novemeber 1998. Also called Zarya, which means sunrise. It contains the propulsion, command and control systems.
Unity
The first US module, Unity. was launched on the Space Shuttle two weeks after Zarya. It is station's main connecting module with six ports.
Russian service module
The 13 metre (42 feet) service module, Zvezda, contains the living quarters, power control and life support systems for the first ISS crew. It consists of three pressurised compartments and has 14 windows.
Columbus Orbital Facility
This module, built by the ESA, will serve as a pressurised laboratory and will provide transport vehicles to supply the station, called Automated Transfer Vehicles.
Robotic arm
Canada is providing a 17 metre (55 feet) long robotic arm called the Mobile Servicing System.
Japanese Experiment Module
The National Space Development Agency of Japan is building the JEM which will provides a pressurised laboratory and an external platform for up to 10 unpressurised experiments.
Brazil
Six items, used mainly for carrying cargo will be provided by the Brazilian Space Agency.
Summarised from the bbc web site