Simply use the charger from Nokia supplied with the phone, Nokia chargers are known to charge 2x as fast as others. It seems to be the case for me so far as well, the Nokia charge pumps in charge really fast.
You're joking right? I've used the Nokia wall charge for my Lumia since the day I got it and it takes longer then my iPhone 3GS took to change when I plugged it into the PC. I think it's just going to take 3 hours to charge this stinking battery for the rest of the phones life.
The 900 has a bigger battery than other phones. Put phone in airplane mode, though has limited or no use while charging. Love the phone, so figure just plug in every night or while on computer.