Listmania!
A physicist's bookshelf
Mathematical Methods for Physics and Engineering: A Comprehensive GuideMathematical Methods for Physics and Engineering: A Comprehensive Guide by K. F. Riley
Buy used from: £28.50
The only maths book (maybe) you'll ever need
Introductory Statistical MechanicsIntroductory Statistical Mechanics by Roger Bowley
Buy new: £29.79 / Used from: £23.00
Superb introduction to Statistical Mechanics...
Quantum MechanicsQuantum Mechanics by Alastair I.M. Rae
Buy used from: £20.00
A nice book on quantum mechanics; doesn't cover everything, but is fairly comfortable going
The Cambridge Handbook of Physics FormulasThe Cambridge Handbook of Physics Formulas by Graham Woan
Buy new: £19.28 / Used from: £17.35
A really useful collection of physics formulae... Doesn't always have exactly what I want, though!
Schaum's Mathematical Handbook of Formulas and Tables (Schaum's Outline Series)Schaum's Mathematical Handbook of Formulas and Tables (Schaum's Outline Series) by Murray R Spiegel
Buy used from: £8.88
Another book of formulae, this time mathematical. Want to solve some hideous integration problem? Look in here...
Contemporary College Physics: 2001Contemporary College Physics: 2001 by Jones
I've got the old edition of this, and have found it very useful over the years - well-written and intelligent