Intuitive Biostatistics
by Harvey Motulsky, Oxford University Press, September, 1995.
ISBN 0195086074. List price: US$34.95.
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Written by GraphPad's Harvey Motulsky, this a great first place to learn about statistics. Focusses on principles of understanding what statistics mean, and doesn't include a lot of mathematical explanations. More info and five online chapters.

Primer of Biostatistics
by Stanton S. Glantz and Stanton A. Glantz, McGraw-Hill/Appleton & Lange, 05 November, 2001.
ISBN 0071379460. List price: US$39.95.
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Wonderful primer that really explains how basic statistical tests work. The explanations of ANOVA and power analysis are particularly great. Nothing about multiple, logistic or nonlinear regression. Little epidemiology. About half the breadth, and twice the depth, of Intuitive Biostatistics.

PDQ Statistics
by Geoffrey R. Norman and David L. Streiner, BC Decker, 15 January, 1997.
ISBN 1550090763. List price: US$24.95.
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Very short, yet amazingly comprehensive. This book is fun (and funny) to read, with clear explanations. Unique and highly recommended.

Biostatistics: The Bare Essentials, Second Edition
by Geoffrey R. Norman, David L. Streiner, and Norman Streiner, BC Decker, 15 July, 2000.
ISBN 1550091239. List price: US$39.95.
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Same style (and authors) as PDQ Statistics, but longer and more detailed. The humor doesn't work quite as well in the longer format, but it is still a great place to learn the principles of statistics.

Multivariate Statistical Analysis: A Conceptual Introduction
by Sam Kash Kachigan, Radius Press, June, 1991.
ISBN 0942154916. List price: US$29.95.
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Don't let the word "multivariate" in the title deter you. This is a great introduction to statistical principles. Includes a great chapter on principles of probablity. And, yes, the last few chapters do explain what multivariate statistics are all about. This book does a great job of explaining the principles of statistics, but is weak on applications to biology and interpretation of statistical results.

Practical Statistics for Medical Research
by Douglas G. Altman and Douglas G Altman, CRC Press, 22 November, 1990.
ISBN 0412276305. List price: US$69.95.
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Lots of clinical examples. Clear nonmathematical explanations, but also includes equations for doing the calculations yourself. Especially clear explanation of how to analyze survival curves. Highly recommended as a second statistics book, once you have read one of the shorter ones.

Biostatistical Analysis (4th Edition)
by Jerrold H. Zar, Prentice Hall, 08 October, 1998.
ISBN 013081542X. List price: US$92.00.
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I wouldn't recommend this book as a place to learn statistics, but it is a very valuable comprehensive reference  book. It covers all aspects of biostatistics, except survival curves. Doesn't have as much personality as the other books listed here, but contains a more complete set of tables and equations than the others.

Statistics (5th Edition)
by William L. Hays, International Thomson Publishing, January, 1994.
ISBN 0030744679. List price: US$99.95.
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Written for social scientists, not biologists, so don't expect biological or clinical insights. The strength of this book are its incredibly clear explanations of the mathematical basis of many statistical tests, especially ANOVA. Nothing about nonparametric tests, survival curves, or nonlinear or logistic regression. It has a unique style that I really appreciate (but others feel very differently -- see the reader's reviews on amazon.com). This is not a good place to start to learn statistics, but is a very good second or third book to really master ANOVA and other topics.