Lodish H., et al. Molecular Cell Biology. 4th ed. W. H. Freeman & Co., 1999. ISBN: 9780716731368, is recommended for those interested in learning more about cellular biology. A limited online version of this book is available through the National Library of Medicine, National Institutes of Health.
WebPath is a great resource for "flipping through" numerous jpeg images of normal and abnormal human tissues and organs.
For those with access to Internet Explorer, a nice Virtual Slidebox of histology and pathology is available from the University of Iowa Department of Pathology.
If you need to look up a medical word, you can search for it online in the MedlinePlus Medical Dictionary provided by the National Library of Medicine, National Institutes of Health.