"Blue Pharm Book" (which incidentally changes color every year) is Tarason's Pharmacopeia. Its very useful as is the Sanford (ie, "Chinese Letters").
Maxwell's very useful, as are the Tarason's and the Intern Pocketbook Series (ie, they have them for Emergency Med, ICU, CCU, Surgery, etc.) - range from $7.50 to $13.00.
If you want something more substantial, the following "handbooks" are very popular:
Surgery - Mount Reid and the Cleveland Clinic Surgical ICU Handbook
Peds - Harriet Lane, Washington Manual
Medicine - Washington Manual, Care of the Medical Patient
Psychiatry - can't remember what I used
Ob-Gyn - ditto