I'm working on a project to build a 16-digit (2 lines of 8-digits) LED display using 14-segment common-anode 2digit units like this-- http://www.mouser.com/ProductDetail/Kingbright/PDA54-12YWA/?qs=sGAEpiMZZMvkC18yXH9iIqAoSpfMDISewf4mMu3f3gY%3D
While I'm sure I could probably build something similar in character count for less money and hassle, I kind've have my heart set on the idea of using these LED displays. I like the way they look and I like the color. The display is going into a car, and as such it will have to operate on ~12-14.5V power. The intention is to have an ATmega328 controlling this display and responding to commands over a car-wide I2C bus (using something like an NXP P82B715 I2C extender to help the bus operate over the whole length of the car) to update the display. I will then have 1 other device, probably with a rotary encoder (to allow the user to switch among different displays) actually sending the commands to drive the display.
In any case, after breadboarding a sample of that 2-digit 14-seg yellow LED display I noticed it looked a little dim when you drive it properly at 1/4 duty cycle for each LED (common-anode, 4 anodes total, each one covering 1/2 of 1 digit) although I was using a 74HC595 driving it with 5V from the Arduino board, not sure if the current really ramped up. Luckily, according to the data sheet, they say you can drive each LED short-term at up to 140mA to achieve high brightness, so I was thinking of using TLC5917 constant-current LED drivers to drive these suckers while the Arduino shifts some high-current-capable darlingtons or MOSFETs or similar.
The problem I have is with power. I thought maybe switching the full +12-14.5VDC through the anodes and using the TLC5917 to manage current would be acceptable, except the maximum power dissipation is a little hideous--consider 8 segments (7 + dot pointer) times 8 displays running at once (2 digits each, but only 1/2 of 1 digit active at any point in time) times, say, 100mA -- that's 6.4A, times 14.5VDC it's 92W. Wow. Don't think I want to set my car on fire by accident...
A far more manageable solution IMO will be to use a Switching mode power supply, say, 5V (which will then provide power to the ATmega328 circuit too). At 5VDC, we're talking 32W (5V*6.4A). Now to be fair it won't run this hot all the time since most of the time segments will be turned off/entire digits blank/etc, but I'm doing the right thing and engineering for worst-case scenario.
Does anyone think I should go lower in voltage (peak fwd voltage of those LEDs is 2.5V according to the datasheet) or just find a switched-mode DC-DC regulator that can handle the load? I found this which looks promising-- http://www.mouser.com/ProductDetail/Murata-Power-Solutions/NEF0100501B0C/?qs=sGAEpiMZZMtwaiKVUtQsNRzjbVtspr5i0nwnBWiI%252bn8%3D
A bit pricey at $20 but it's worth not starting a fire on the dashboard of a moving car 
Or is the whole idea truly hideously out of line?