I've been pondering this current-limiting nonsense all day, and I think I'm overthinking.
The issue is this: If I want to get maximum brightness out of my LEDs, I'm going to want to overdrive them a bit because I can run them at a maximum of33.3% duty cycle (if I have three LEDs lighting up at the same time). LEDs that are rated for 20mA of constant current might be rated for up to 100mA of peak current. Apparently, nobody make a 40+mA constant-current LED driver that runs at 3V. Oh well.
I think I'm going to bite the bullet on this one, and I think I'll be okay. I ordered a bunch of 0402 LEDs to play with (they're very very very small). I want to see how bright they are and how much abuse they can take.
I also ordered some banana plug binding posts so I can convert an old ATX power supply to a lab power supply.