I have planned to make robot that is controllable from my computer on web browser. The problem is that i dont know how to make arduino communicate with computer. Do i need ethernet shield or something?
It depends on how you plan to make the robot move around.
If the robot can have a cable to the computer then you can just use the normal USB (which really is a serial port).
If the robot can not have a cable to the computer then you need some kind of wireles either radio freq. or wifi (or bluetooth or IR - maybee)
There are many ways to connect the Arduino to the Internet.
Ethernet is one. There's also a WiFi shield available from asynclabs.com.
There are also lots of ideas on this page.
How big is the robot?
I'm in the (sloooow) process of building such a robot; my platform is a PowerWheels Hummer H2. So, I have an on-board PC (Intel ATOM mobo with 500 gig of HD space) connected to an 802.11g router for communication (just open up a browser to the web server running on the ATOM), then the PC will communicate to the Arduino (which will initially handle control of the steering, drive motors, and communications to the servos for a pan/tilt camera mount) via a USB cable.
This kind of system could be easily scaled down to a smaller sized robot (ie, something the size of a medium-sized trash can); you wouldn't have to use an ATOM mobo with 500 gb of space, either (design goals of doing on-board real-time vision processing using OpenCV kinda dictated the beefy system). You could, for instance, pick up a cheap old mobo and wifi router from a thrift shop (unless you live in Denmark, I suppose).
An old 486 or Pentium, with a smallish old PATA laptop harddrive and a wireless-b router would work great, and be dirt cheap (under $100.00).
You would still need a good power supply for all of this (in my case, I am going to have multiple 12VDC gel-cells - but you could probably get away with anything provided you can deliver enough current and the proper voltages - for instance, I am using a small DC-DC PicoPower supply meant for car pc installs).
Good luck with your project!
There are numerous ways to use bluetooth or zigbee adapters to wirelessly communicate between a computer and a board/controller on a bot. An apache web server can be used on the computer to act as a web interface for brouser control. Another approach could be to put a computer on the bot itself like below. The ethernet shield approach would be somewhat more involved, but would remove the pc from the bot control.
Hey cr0sh, what kind of vision processing are you going to do? I just recently found harpia: http://sourceforge.net/projects/s2ilib/ and http://www.3d-webcam.net/ I wonder if that can replace an expensive laser range scanner?
As to the communication, I also thought about using the freerunner http://openmoko.com/freerunner.html. That way the robot wouldn't have to be in the range of a wifi. But the driver for the USB-Serial converter used on the arduino is not in the standard kernel of the debian based freerunner distros. So, one would have to compile the kernel. What does work out of the box however is to communicate to the freerunner over the internet, and with bluetooth from there to an arduino bt.
Another good low powered Pc is the alix : http://pcengines.ch
I have made some new plans and maybe it would be much usefull if i could use the robot with my phone. I will need some bluetooth shield, right? And then i need to make a program to my cell phone. There would be enough challenge ;)