"Robots", a term coined from the Czech play "RUR", have been part of the Toy world for a great many years, mostly from the amusing automata seen in the victorian era, leading on to the clock-work tin Robot toys of the early to mid 20th Century to the phenomenon of the Robot Pet of the late 20th and early 21st centuries.
Included in this group of toys should be the construction sets, many of which were pressed into use as cars, planes, rockets and robots but were designed to create models of buildings. The two most famous construction set systems still active today must be the once British, now French, MECCANO™ and the Danish LEGO™.

MECCANO™ - has been the by-word for modular construction systems for over a century, its bolt-together perforated steel strip and plate style parts have been the starting point for budding mechanical engineers worldwide, allowing the building of complex working models of many real world devices and vehicles. However, in the early 1960s the LEGO™ company made inroads into this market and virtually took it over when it introduced the LEGO TECHNIC™ system. This was due in part to the use of push fit type connectors rather than the nuts and bolts used by MECCANO™ - the bane of many a MECCANO™ modeller even today. LEGO™ today have even created a Robot design System, the LEGO MINDSTORMS™ which has become a standard robotics teaching and research tool in schools and universities world wide.
From the point of view of building robots the LEGO™ system is good, but it is difficult to build a robot which will not fall apart at every opportunity since few people will have the neccessary specialist LEGO TECHNIC™ construction skills
On the other hand to build from the standard MECCANO™ can be frustrating as most of the nuts used do not lock and soon loosen as the construction proceeds - However the use of alternative Lock Nuts and Bolts makes a world of a difference especially if a small ratchet spanner (wrench) or Socket Set is used
Thus the use of MECCANO™ or a similar system allows a strong and even large structure to be constructed and operated for a long period without the need to rebuild.

Other construction systems are on the market some with the sole aim of building robots.
In the toy market the most notable are ROBOTIX™ and CYBER K'NEX™, which allow the creation of self powered models of many sorts. CYBER K'NEX™, however does have a level of pre-programmed functionality giving character to the different set models provided.
In the education market LEGO DACTA™ is a leader, and a newcomer from the USA takes the mechanical modular concept one step further having fewer types of components this is - ROBIX™

Some interesting results can be obtained using a mixture of construction sets - each having its own particular strong points.

Not many of the complete TOY ROBOTS have succeeded in the market place - often due to unrealistic expectations from manufacturers and the "one season to be successful" approach.
Some examples are R.A.D.™, a large tracked robot which saw 4 different versions in as many years, the first being the best.
The most tragic example is that of I-Cybie™, a robot dog/pet which came after two years of poor and very cheap imitations of the SONY ABIO™ which retails at around 900 Pounds Sterling, the I Cybie was 179 Pounds on the runup to Christmas 2001 but dropping to 75 Pounds just before Christmas.
This very functional walking robot is now available for around 50 Pounds and the original manufacturer has now brought out a series of accessories, including a walk-up-charger and a downloader for software from a PC, making it the best value real robot dog on the market.
The SONY AIBO Robot dog has by far the highest specification, but at 1500 Pounds for the Dog and accessories is for serious Robot enthusiasts only and has few rivals in any other field of Mobile Robots.

The field of BEAM robotics and the Nervous Net patented by Mark Tilden is now repesented, not only by specilised kits, but by the mass produced BioBugs™. These were designed by Mark Tilden on contract to the toy maker Hasbro and appeared in the 2002 toy season.

Some of the best Robots produced are the ELEKIT™ range which are all mobile robots except for one static Robot Arm or manipulator. These robot kits are mostly manufactured from Polycarbonate ( like Police Riot Shields ) and have a range of sensors and modes of locomotion producing varied and interesting behavours from a pre-soldered circuit board.