Hey,
Good to hear you're trying your hand at micro's, they can be very handy indeed!
The usual way to 'fade' an LED, whether that is fade in or out, is to use PWM (pulse width modulation). That involves turning the LED on and off, very quickly, but varying the duty cycle, the ratio of on time and off time. The eye averages the brightness, meaning a 10% on time, 90% off time, the led is faint, but at 90% on time, 10% off time, its bright. The period however, remains the same.
There are various methods to do this with a PIC, many discussed in this forum, and many PIC's have one or sometimes two built in peripheral modules, that handle it all for you, you simply configure it for a frequency, and duty cycle. Using a timer, or a delay routine, you can periodically increase the duty cycle by a certain factor (which will determine how smoothly it fades).
Software methods, that don't involve dedicated hardware use timers/delays to achieve the same effect, not always efficient if the PIC in question is doing many other things, but for a dedicated task the programming can be relatively straightforward. Thats why I, and many others, suggest PIC's for this in the first place
With one of the limitations of a microcontroller being the pin count, number of I/O's, you would only need 3, one input (for triggering the 'photon torpedo firing' and two, outputs, one for each led. So an 8-pin pic would be more than adequate, preferablly one ith an internal oscillator, reducing the part count/cost even further. Part numbers that spring to mind are the 12F509, 12F510, 12F629 or the 12F625. Or, if you need other tasks contorlled at the same time, like a master controller, a larger 18-pin one like the 16F628A.
I'm still convinced a 'analogue' circuit could do it, but if you're willing to stick at the PIC programming, it'll allow you to modify the effect whenever you want, make significant modications, and add many other goodies to it (like programmed firing sequences). The limit for that is code space, and I can't see it taking up more than a few lines, so 40 sequences would easily fit on a small 8-pin job.
I'm away for a few days next week, hopefully I'll have some time for testing something, just incase a 555 timer is up to it, plus, I'm surrounded by LED's here (buying them up has become a habit/problem) so I need to justify their existance.
Blueteeth