Maps for everyone:

Ordnance Survey Explorer OL36 South Pembrokeshire Map.  This comes in two varieties - the normal paper variety linked to here, plus an Active version that's a bit more weatherproof.  The scale is 1:25000.  Features are twice the width and height on this map compared to the Landranger, but the map only shows about a quarter of the area. (Available in Dial Cottage)

ORDNANCE SURVEY Landranger 158 Tenby & Pembroke Map.  Also comes in two versions.  The scale is 1:50000. (Available in Dial Cottage)

Map for North Pembrokeshire:

Ordnance Survey Landranger 157 St David's & Haverfordwest Map.  There's a lot of overlap with 158, listed above. (Available in Dial Cottage)

For coastal footpath walkers:

The Pembrokeshire Coast Path (UK Long-Distance Trails).  This is a full-on set of walking notes, and contains its own map.  I think it's seriously worth looking at.  Take care to buy the correct version of this book, though.  Even if you're just dabbling with the coast visitors have found this a very useful book for planning. (Available in Dial Cottage)

Also:

Pembrokeshire Coast Path: Trailblazer British Walking Guide

Pembroke Coast Path (Route Map) A map of the entire path, printed on weatherproof foldable polythene.

Pembrokeshire South: Circular Walks Along the Wales Coast Path (Top 10 Walks: Wales Coast Path

Pub Walks Pembrokeshire : Walks to the best pubs in Pembrokeshire (Pembrokeshire: Top 10 Walks)

Walking in Pembrokeshire: 40 circular walks in and around the Pembrokeshire Coast National Park (British Walking)

For cyclists:

South West Wales Cycle Map (National Cycle Network Route Maps

For climbers:

Pembroke Rock (Wired Guides) - 1000 Selected Rock Climbs

Pembroke: Rock Climbing Guide (Rockfax Climbing Guide)

For beachcombers and young botanists:

Guide to the Common Seashells of Britain and Ireland (Chart)

Key to Plants Common on Sand Dunes

Guide to Summer Coastal Birds

Guide to Woodland Plants

Shells (Usborne Spotter's Guide)

RSPB First Book of the Seashore

Sandcastles Made Simple: Step-by-step Instructions, Tips, and Tricks for Building Sensational Sand Creations

Local interest:

Pembroke & Around Through Time

Pembroke Dock Through Time

Memories from Pembroke Dock

Local history:

Lamphey Bishop's Palace - Llawhaden Castle: Carswell Medieval House - Carew Cross

Pembroke Castle: Birthplace of the Tudor Dynasty