For me: Perry's Chemical Engineering Handbook Transport Phenomena (BSL) Coulson and Richardson Vol. 1 Fundamentals of Momentum, Heat and Mass Transfer (WWW)
Right now I'm just using information from them for my third year project. They would have been useful to me much sooner if I'd done relevant questions though in first and second year. After deadlines and exams I might start making myself read them and do questions in them though, just to increase general chem eng knowledge. Couldn't hurt