Custom DAC for Arduino UNO I am currently following this tutorial on building a Simple Audio Player for the Arduino. I was about to finish the circuit only to realize that the required board is an Arduino Due and I have the Uno. 

Because the Uno does not have its own DAC port, I was wondering what other options are available for me to accomplish the same thing while keeping the circuit as similar to the one listed in the tutorial.

Thanks
There are three basic ways of creating a DAC.

The simplest, though roughest, is to use PWM, then low-pass filter it.  Not perfect, but rough and ready. Only needs a resistor and a capacitor.

The highest quality way, though slowest for interfacing, is to use an external DAC chip. Fine for low frequency response reproduction, and the linearity is second to none. The MCP4821/2 is a popular choice (SPI connected).

The third option is to build your own DAC using an R-2R ladder. You can make an 8-bit DAC with very fast response by using all 8 pins of a single IO port (such as pins 0-7 on the Uno are bits 0-7 of port D). However the linearity of an R-2R ladder very much depends on how well matched your resistors are.

The R-2R ladder should be buffered with an amplifier of some form before driving a low impedance device like a speaker.

None of them are really great for audio work - for that you need a chip with much more processing power and memory, and a high speed digital audio interface, such as I2S, to interface a proper audio CODEC chip. Personally I use PIC32MZ chips for audio work.