EDIT: I have my BreadboardsBut here's a few ways to go at it to fade LEDs:
Schematics will be Posted Later for you people.
X Option 1 "The easy way out":Put a RC circuit on paralell with the LED.
As the power source is removed, the charge stored in the capacitor is slowly bled through the LED.
Cost Approx: $4-$6
Most Expensive Component: Capacitors
Video Presentation:Fading an LED With a Resistor-Capacitor CircuitSchematic:================================================
X Option 2 "PICs":Get a PIC and program it to fade, but most people don't have the time and ethic to do this.
Pretty Reliable, your best bet here to conserve battery life.
Cost Approx: $2-$5
Most Expensive component: The PIC
Video Presentation:Schematic:================================================
X Option 3 "D/A Converter":a 4017B Chip can be used as a digital to analog converter to fade the LED with resistors to comply with 10 different variations of resistance to suit your needs to fade an LED with smooth clock pulses that are easily controlled by a 555 timer.
This way is Semi Cost effective, sometimes reliable, but not the most compact design. (too many resistors) and Most importantly its possible to be Multi-functional and will drive 10 Separate LEDs
Cost Approx: $4-$10
Most Expensive Component: Resistors
Video Presentation:PART 1 THEORY:
4017 Basic Theory to Fade an LEDPART 2 IN ACTION:
4017 Fade an LED CircuitSchematic:================================================
X Option 4 "Delayed Pulse Generator":Currently I'm Working on this one. It is a Very Cost effective and good for beginners. Only requires 2 of the notorious 555 Timers and a few resistors and 4 caps.
Cost Approx: $3-$12
Most Expensive Component: 556 Dual Timer or 4017 Decade LED Driver Counter
Video Presentation:Schematic:===========================================