Programmable robots\\designers?

Doing the right thing by the Arduino. This thing makes it very easy to understand what is a microcontroller and realize the awesome range of capabilities that they offer. At it without frightening words like "programmer", "assembler", etc.
The language is extremely simple. Yes, it is made on the basis of the si, but the team there is quite obvious and the examples he mastered overnight. While not losing the ability to scale.
In his time he was interested in a similar question, Insel such cool thing as IE-POPBOT (link to the store: www.terraelectronica.ru/catalog.php?ID=1171&ClearParam=1 link to pdf description: www.terraelectronica.ru/pdf/INNOEXP/IE-POPBOT.pdf). This is the finished robot on the basis of audini with a set of sensors which allow to implement programmes of the Autonomous riding on flat, taking into account various obstacles (sensitivity to the walls, the cliffs, the contrast color on the surface, etc.). Further, learning to do the standard things according to the instructions, You will not be difficult to come up with something of their own. In General, the space to play is very great, and probably encourage more in-depth study of individual aspects and sosednie something completely different and its very cool :)

LEGO, of course, cool, but too expensive, and benefit from trials with the Arduino much more.
Just decide what is more important — to make the toy from constructor ready or know and be able to.
Here's a wonderful collection of articles about Arduino:
\rrobocraft.ru/page/summary/
Success!

About the Arduino — I can advise the next option. There is a similar Board, opportunity Board, however, working on .NET. I think, for them, the barrier to entry is much lower, plus tasty snacks type convenient IDE (VS Express Edition), debugging, and dot-netovskih libraries.
View here: www.tinyclr.com/

Toys + Chip and Dip + AVR. Things you can collect

"Humanoid Robots" www.rusandroid.ru/

the ideal — LEGO Mindstorms NXT 2.0, and the price is 12000 for a set of 4 sensors, 3 motors, module, +500 parts in my opinion is quite normal, especially since you can purchase only what you need for parts.