Mark -
There are a few I recommend:
1) Tarascon (sp?) has a little lilac colored book that gives great tidbits and dosages; nothing that you can really sit and sink your teeth into, but gives you rapid facts. Cheap and tiny. Worth it in my opinion.
2) Marino's "Little ICU Book" (or some such name; aka: Baby Marino). Condensed version of the Marino ICU Book that I assume you are reading from; small enough to carry, and deep enough to sit and read during downtime. I didn't use it on my med student rotations, but there was an intern that was reading it and he looked like a frickin' rockstar (cannot guarantee you the same results, but he said it was a great book).
3) Critical Care - I have no idea the actual name of the book; it's green and written by a surgical resident. There was a thread on this very subject several months ago, and I think I named it there. It's the one I used - bullet point format, which I loved after an admit - I'd create my differential, look up the big ones in that book, and then I'd have an idea of the pertinent clinical things and labs to get and treatments. Very nice. Narrow enough for the lab coat pocket, but thick.
Good luck with things.
dc