I am working on an Arduino project where I need more digital and analofgpins than the Uno offers. I was wondering how to hook up multiple Arduinos (4) together so I can use their digital and analog pins. Thanks in advance.
I suggest using a single Arduino Mega. It offers 54 digital I/O and 16 analogue inputs.
I suppose you could also use I2C or SPI to communicate between multiple Uno's.
Ryan Griggs' suggestion of the Mega is likely to be easier and more economical than using multiple Unos. That said can you say more about what you want to do with your proposed design? There are good reasons for distributing the load and the problems are interesting – so it is not obvious that the "right" answer is just to use a bigger central machine.
Besides tightly coupling them with the SPI or I2C you could also consider using Ethernet or Bluetooth. Arduino Ethernet shields tend to be expensive, but there are some wireless devices like the Adafruit Huzzah that are more economical.