There are 17 tutorials to build Arduino Web Server. Makers can learn From the Basic Web Server to the Advanced Web Server.
I made a weather station connected to the internet. It measures temperature, humidity, UV index, rainfall and it calculates few more important meteorological values. It then sends this data to weathercloud.net, which has nice graphics and UX. It also has a weather web camera. It cost me around 150€. I made this station as my school project.
Wiring the WIZNET W5100/W5500 as Network Time Protocol Client with Microcontroller