The Welsh Hedgehog Hospital - has a lovely site with a particularly good page on making a wildlife garden. Was offline last time I looked but could anyone who knows the new site let me know.
Froglife is a charitable organisation that works with volunteers, ecologists, government departments and the public to conserve the native amphibians and reptiles of Britain and Ireland. This is a very good place to start if you want information on the frogs, newts and toads in your pond.
Faunagarden - stock a variety of wildlife habitats for birds, frogs, insects and mammals. I have their frog house and a couple of different insect habitats in the garden. Choose Product Range and then Habitat links.