I’ve recently started working with the ESP8266 model ESP-1 Wi-Fi web server, web client and access point. It is an incredibly powerful microprocessor with an equally powerful Wi-Fi radio. Its 32 bit, 80 MHz processor has lots of memory (compared to my ATMega328) and at around $2 US, its hard to beat.
You can use several different development environments but the ESP8266 community has ported it to the Arduino IDE. I’ll post a few of my most recent prototypes in the next couple of days.