Web interface project.
It has many input and ouput (GPIO) but no IP connectivity.
Arduino needs external power to run
Arduino is not a computer
You can make a mini webserver with arduino but it will be difficult to keep it stable.
Memory limit, calcul ressources and so on
With the right shield plugged in your Arduino or an ethernet Arduino, you can relatively easily connect your Arduino to the web.
You can find shields for less than 20€ (august 2014).
In practice, I could not manage to make a program that can run more than few days (one week maybe). It is sometime hard to debug and find why Arduino has "crashed" or not but could not respond until your reset it. :(
Wifi shields seem to be more than 50€ ... too expensive for my project.
I have not tested wifi with Arduino because I cannot have stable ethernet program.
Arduino & Raspberry or Raspberry only ?
Why I do not use Raspberry
At first look Raspberry project is "sexy". Not so expensive, a real but pretty slow computer with GPIOs.
It is said to run Linux, to be an open source and educative project.
I was happy to receive mine because at this time my Arduino project reveals itself to be too difficult (cf: ethernet connectivity).
Raspberry project is well sold if your read its website.
I was a bit confused when I try to read data from my DHT11 sensor, It was so easy with Arduino, It should be a least as so easy with Raspberry ?
I have found a driver for DHT11, a Linux kernel driver, It was not my first compilation, I was confident.
Make complaint about kernel headers, I have to find this files, apt-get is your friend, isn't it ?
I do not know why I have not felt on this page https://wiki.debian.org/RaspberryPi but I recommend it before starting a project with Raspberry.
Arduino & OpenWrt
I was looking for an IP conectivity, ethernet or maybe a wifi connection.
I have found a page about a mini AP/Wifi router for half a price of a wifi shield...
Damned! I can connect my arduino, power it via 5V USB plug, with a little router ???
Fantastic, OpenWrt rox !!! I am loving it :-) <3 \o/