so i did this before for a robot in my work office.
the idea was to have an internet controllable vehicle that co workers in other locations could log into and drive around the office.
there was a little LCD display on the front for typing out messages too.
i won't go into the construction of the bot here. suffice to say it was PIC based and was connected to a PCs serial port via a pair of easy-Radio modules. http://www.lprs.co.uk/main/product.info.php?productid=154
(i think there are cheaper options on the market now but i can still recommend the easy-Radio transceivers as being fairly simple to get working.)
it had a camera on there as well that transmitted the picture back to a TV card on the PC via a wireless video sender but i'm only going to talk about the controll aspect of it here.
so once you have a robot controllable over the serial port, here's the theory behind making it web controlled.
you will need a computer running a web server that has a serial port. (duuh.)
you will also need some sort of programming/scripting language that can be executed by your web server as a CGI. (a CGI is just a script that can be run by your web server, producing some effect other than displaying a web page. a script to send an email from a web page would be an example of a CGI. in our case, we are going to send commands to have our bot move from the CGI.)
i was running Linux with apache web server and using python as my scripting language.
i chose these 3 because i knew how to use all 3.
what i'm describing will work with lots of other operating systems, scripting languages and web server packages.
i'd imagine a lot of other people would be happier using windows with the built in webserver (does windows still ship with a web server package?) and PHP as the scripting language.
alternatively, for those running windows, apache and python can be installed on windows and are open source.
so, the first step is to get your web server up and running and able to execute a small "hello world" CGI script.
next, you want to find out how to access your serial port from your scripting language.
as i was using python, i used the pySerial extension. http://pyserial.sourceforge.net/
in other scripting languages you should be able to do similar. i know it's possible form PHP.
note. if you are using Linux you will have to make sure the computer's serial port has the right permissions to be controlled by the web server. windows users should see no such security.
next, write a CGI script to send the same controll characters to your bot over the serial port as you would if controlling it directly.
so, the robot's not in my house any more and you guys can't access my work network but here's the webpage that used to controll it when it was in testing at home.
**NOTE THIS IS NO LONGER FUNCTIONAL.**
it's just to give you guys an idea as to the interface i'm talking about.http://188.8.131.52/robot/
well anyway, if anyone wants more info, i'll write up a proper tutorial eventually.