you just need to know if there's exist mBTC and uBTC , 1 mBTC = 0,001 and uBTC = 100satoshi if I'm not mistaken ,this really help a lot for few sites
Of course this is the obvious set of units to use.
Take a price in bitcoin:
move the decimal point 3 spaces to the right and you have the price in millibitcoins (mBTC)
move the decimal point another 3 spaces to the right and you have the price in microbitcoins (uBTC)
move another 2 decimal points to the right and you have satoshis
For some strange reason some people like to call a uBTC a 'bit', but there's really no need to add that new unit at all.