Powering Super-Bright LEDs

I need to power 3 or 6 Super-bright LEDs on a robot I'm building. The robot has a rechargeable 7.2v Ni-cd battery which currently powers the on-board processor and some motors. I plan to tap off the battery, but 7.2v is obviously too high.

I saw the LED array calculator at http://led.linear1.org/led.wiz which uses resistors and that certainly helps, but would it be better to use a voltage regulator? If so, why, which and how? I'm pretty sure the LEDs are rated at 3.3v and 20ma.
davidkatAsked:
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CallandorCommented:
If the LEDs are identical, how about wiring them in series?  That way, you don't waste any power on a resistor that does nothing.  6.6v may be close enough to 7.2v to function without damage.
davidkatAuthor Commented:
I would try that, but I need to power three. Is there a way, combining series and parallel to wire 3 leds? two in series, say, and one in parallel with one of those wired in series? What about six?
CallandorCommented:
If all LEDs are rated the same (requiring 3.3v), they have be in a group with the same configuration.  Two in series will give you 3.6v to each, while three in series will give you 2.4v to each.  Mixing the combinations will create different voltages to some.  If you have six LEDs, just set up three pairs in parallel, with each LED in a pair in series.

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davidkatAuthor Commented:
This should work fine. And no lost power to resistors. I'll try it as soon as I can. Thanks!
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