Use RECHARGEABLE batteries for Arduino Diecimilla?

How can I power the arduino with rechargeable batteries?

Can I just use this:

I have 4 rechargeable batteries à 1.2V, so i get a voltage of 4.8V. Does it work or does the arduino need 5 or 6V?

You need about 6.5 to 7V to power the board through the regulators. If you power this directly then you might get away with 4.8V but as soon as they start to droop you can expect trouble.

So I could take two battery holders (->link^^) and put them together, which would provide max. 9.6V. Probably it will be about 9V to 9.2V after some time? Is this higher voltage bearable for the arduino?

Or shall I get a 4 AA and a 2 AA battery holder and put them together, to get 6x1.2V= max. 7.2V?
It gets kinda big, but the standby time will be huge, won't it?

I have 2500mAh Ni-MH Rechargeables. So 6*2500= 15000mAh. ;D
So disadvantage is the size, but the advantage is the huge capacity?

You could also use this . . .

and connect directly to the 5V pin. I've used it with good results.

Yep any of those look good. I especially like the little step up from Sparkfun.

The closer to 7V you get it the less power you waste. The input voltage can be at least up to 15V so don't worry about 9V being too high.

If you took a look at my "buying list" for now I do not want to buy from sparkfun too. Probably in one month or two I will buy a couple of other items. But I do not want to pay additional shipping charges there too. :-/

Can I do it the way I have proposed? 4 AA + 2AA battery holder? (Or 2x 3AA battery holder?) Will that work?

As long as your input voltage is within the Arduino spec for input voltage, you'll be fine.