A Treasury of Knitting Patterns, A Second Treasury of Knitting Patterns, and
Charted Knitting Designs - Barbara Walker
(These books also changed my life. They should be in every knitter's library.)
The New Knitting Stitch Dictionary - Leslie Stanfield
(This book presents beautiful stitches in chart form.)
The Knitting Dictionary - Mon Tricot
(This is old and hard to find, but definitely worth the search - a great stitch book!)
Big Book of Knitting Stitch Patterns - Sterling Publishers
(This is a new book and is excellent.)
All Harmony Knitting Guides
(There are about 6 books in all, and all are wonderful.)