8-segmet LED's on Adafruit Trinket
For LED displays, I advise using a MAX7219.

This circuit:


can manage up to 8 digits (7-segments + 1 LED for DP or colon separator) or up to 64 LEDs
needs only 3 pins to manage display
can be daisy-chained if you need to interface with more than 64 LEDs
requires only 1 resistor to be fully functional
is easily supported on Arduino with this library


I have used it in several circuits and happy with it.

Note that there also other libraries that support this circuit but I haven't used them.

This circuit has only one downside: its price (about $10 each); but the price is counter-balanced by its simplicity and the fact you don't need any additional component (e.g. transistors) besides a simple resistor.