Given the International Space Station's modular design, it appears spacecraft such as Soyuz and resupply freighters such as Progress can attach to many different modules.
This NASA diagram from 2008 shows Soyuz can be attached to four modules:
- MRM1 (Mini Research Module - Rassvet)
- MRM2 (Poisk)
Here's a 2008 NASA photograph showing two Soyuz craft attached to the ISS. The angle makes it look like they might be attached to one of the US section modules, but in fact they are docked to Pirs and Rassvet. The caption reads:
ESA's Columbus laboratory, Node-2 and Japan's Kibo module at the ISS (main truss at rear, two Soyuz vehicles lower centre)
Here's another NASA image from April 2014 showing two attached Soyuz, captioned:
There are now four vehicles, two Soyuz spacecraft and two Progress space freighters, docked to the International Space Station.
A good question and answer similar to this is the question:
Will the ISS need more docking ports?
Some details on the Russian and US segments future plans as well as current situation is available in that question.