The most useful robots onboard currently are the SSRMS and JEMRMS, both are teleoperated robotic systems.
The JEMRMS (Japanese Experiment Module Remote Manipulator system) is
a 10m long robotic arm, mounted at the port cone of the PM, intended
to service the EF and to move equipment from and to the ELM. The RMS
control console was launched while inside the ELM-PS. The main arm was
launched with the PM. The "Small Fine Arm", is 2m long and attaches to
the end effector of the main arm, was launched aboard.
(from Wikipedia) Acronyms: PM - Pressurized Module, EF - Exposed Facility, ELM - External Logistics Module
The SSRMS (Space Station Remote Manipulator System)
Launched on STS-100 in April 2001, this second generation Canadarm is
a larger, more advanced version of the space shuttle's original
Canadarm. Canadarm2 is 17.6 m (58 ft) when fully extended and has
seven motorized joints. It has a mass of 1,800 kg (4,000 lb) and a
diameter of 35 cm (14 in). The arm is capable of handling large
payloads of up to 116,000 kg (256,000 lb) and was able to assist with
docking the space shuttle. Officially known as the Space Station
Remote Manipulator System (SSRMS), it is self-relocatable and can move
end-over-end to reach many parts of the Space Station in an
inchworm-like movement. In this movement, it is limited only by the
number of Power Data Grapple Fixtures (PDGFs) on the station. PDGFs
located around the station provide power, data and video to the arm
through its Latching End Effectors (LEEs). The arm can also travel the
entire length of the space station truss using the Mobile Base System.
Most of the time the arm operators see what they are doing by looking
at the three Robotic Work Station (RWS) LCD screens. The MSS has two
RWS units: one located in the Destiny module (US Lab module) and the
other in the Cupola. Only one RWS controls the MSS at a time. The RWS
has two sets of control joysticks: one Rotational Hand Controller
(RHC) and one Translational Hand Controller (THC). In additional to
this is the Display and Control Panel (DCP) and the Portable Computer
System (PCS) laptop.
Note that no one involved with the SSRMS ever refers to it as the Canadarm.