the root of the second site--
http://pedsccm.wustl.edu/ is good to peruse.
for basic stuff, i would read up on your physiology. acid/base, blood gases, ventilation, frank-starling type stuff. then i'd brush up on your ID (lots of spetic-ish and empiric abx in the PICU) and stuff you don't normally use in regular peds, like vasoactive meds and their indications.
PICU is fun if you go into it with the right attitude. be pro-active about procedures-- they're fun
--your friendly neighborhood currently on PICU himself caveman