Field Guide: Rocks & Minerals of the World - D. Cook, W. Kirk
An excellent book for rock and mineral identification from Kingfisher. Highly commended.
ISBN 1-85697-151-1 Amazon

Field Guide: Rocks and Minerals - P. Bell, D. Wright
Another highly useful identification guide for rocks and minerals, with a few pages on fossils. Not as good as the Kingfisher one, but probably cheaper.
ISBN 1-85152-605-6 Amazon

A Golden Guide: Fossils - F. Rhodes, H. Zim, P. Shaffer
The target readership is questionable - this pocket-sized book requires some former knowledge, but is again, very well-illustrated. Over 150 pages and some helpful specimen identification, particularly for North-American finds.
ISBN 0-307-24411-3 Amazon

Fossil Identifier - Scott Weidensaul
An extremely useful, tidy and minimalist guide to help you identify your finds at a general level. Weidensaul writes in an easy but un-patronising way. Highly commended.
ISBN 1-85076-288-0 Amazon

Eyewitness Handbook Fossils - Cyril Walker and David Ward
Absolutely the best fossil identification handbook I've seen. It will satisfy the most experienced of collectors and is beautifully presented. Very highly commended.
ISBN 0-86318-921-0 Vendor

BRITISH

British Caenozoic Fossils - Natural History Museum
Caenozoic fossils!
ISBN 0113100248

British Mesozoic Fossils - Natural History Museum
Mesozoic fossils!
ISBN 0113100256

British Palaeozoic Fossils - Natural History Museum
Palaeozoic fossils!
ISBN 0565056247

Fossils of the Chalk - compiled by Ellis Owen
Fossils of the chalk!
ISBN 0901702366