Introductory Mycology textbooks with good diagrams for identifying oomycetes:
Alexopoulos, C. J., C.W. Mims, and M. Blackwell. 1996. Introductory Mycology. Wiley, New York. Kendrick, B. 1992. The Fifth Kingdom, 2nd edition. Mycologue Publications, Waterloo, Ontario, Canada. Webster, J. 1980. Introduction to Fungi. Cambridge University Press, Cambridge.
Alexopoulos, C. J., C.W. Mims, and M. Blackwell. 1996. Introductory Mycology. Wiley, New York.
Kendrick, B. 1992. The Fifth Kingdom, 2nd edition. Mycologue Publications, Waterloo, Ontario, Canada.
Webster, J. 1980. Introduction to Fungi. Cambridge University Press, Cambridge.
Links to pages that explore oomycetes and their connections to other life forms:
Carlile, M.J. and S.C. Watkinson. 1994. The Fungi. Academic Press, San Diego.
Fuller, M.S. and A. Jaworski. 1987. Zoosporic fungi in teaching and research. Southeastern Publishing Co., Athens GA.
Kendrick, B. 1992. The Fifth Kingdom, 2nd edition. Mycologue Publication, Waterloo, Ontario, Canada.
Margulis, L. and Schwartz. 1982. Five Kingdoms: An Illustrated Guide to the Phyla of Life on Earth. W.H. Freeman and Co., San Francisco.
Schumann, G.L. 1991. Plant Diseases: Their Biology and Social Impact. APS Press, St. Paul, MN. Click here to see Chapter 1: "The Irish Potato Famine and the Birth of Plant Pathology, pp. 1-24.
Sparrow, F.K. 1960. Aquatic Phycomycetes 2nd Ed. Univ. Michigan Press, Ann Arbor, MI.