Check out MedCalc (free), epocrates, lexicomp, ABG calculator... all free
A paid app I use once in awhile is Jaundice. You plug in hours of life, and bili levels, and it tells you based on the nomogram whether to treat or not, and what the exchange level is. It's only for term babies though...although I mentally adjust for preemies.
You may also want to look into getting your textbooks through Amazon
on the kindle
reader app. You can use this app on the computer, ipad, iphone, kindle, etc. If they had this when I was in school 3 years ago, I would've done it. Especially for our giant 2-volume main text, Fanaroff & Martin, which I wouldn't have had to lug around.