1x Arduino. I used an UNO (but any version should work). Make sure it has a 16MHZ timer chip on it, otherwise timer functions will be off (until I update with an RTC [Real Time Clock]. To tell if it has the timer, it should have a silver oblong piece on the PCB, with 16.000 printed on it.
1x Power supply for Arduino (not shown)
1x Breadboard. A half size board will work, but a full sized one is easier to work with (I'm using 2 half size boards together.
Breadboard Jumpers - quite a few are needed.
7x 2N3904 NPN type transistors (maybe 8 for AM/PM support, working on that)
8x resistors. Try for a value greater than 200 ohms and less than 1k. I'm using 220 ohms. (10x if I get AM/PM support)
7x 1k ohm resistors. These will keep your Arduino from overheating (8x if i get AM/PM)
1x 4 digit 7 segment display. I used a common anode display (but a common cathode would work with editing the code). Make sure it has a colon! One used in project- Sparkfun COM-09481
also available in red, green, and yellow (blue costs 50c more than the other colors. I got 2 just in case [but these are almost unbreakable if you remember to use resistors])
*Note that if you want to just build it w/out testing, you don't need the breadboard and jumpers. I wanted to test mine first but I'm gonna build a finished up prototype when I get some other parts.