Forums:
Insectes.org
Lepiforum (Forum)

Photos of Moths and Butterflies:
Les Carnets du Lépidoptériste Français
Lepiforum (Classification)
Lépidoptères de France méridionale et de Corse
Papillons de l'Indre (36)
Papillons du Maine et Loire (49)
6 Pattes - Les Papillons de la Vienne
Lepsibu, my Flickr photostream
Moths and Butterflies of Europe and North Africa
Norwegian moths and butterflies
Butterflies and Moths of Northern Ireland
Euroleps
Lepidoptera and their ecology
Familie Roths Naturfotos

Photos of Butterflies:
Butterflies of America
Butterflies of India
Butterflies of Sri Lanka
Butterflies of The Philippines (Project Noah)
Butterflies of New Zealand
Matt's European Butterflies
Butterflies of Bulgaria
Great British Lepidoptera

Photos of Moths:
UK moths
African Moths
Schmetterlinge aus Oberbayern

Photos of Larvas:
Lepiforum (Larvas)
Ukleps.org
Larvae of North-European Lepidoptera
Raupen

Specialised sites:
La diversité des Heliconius
Zygènes des Alpes Maritimes
Cahurel-entomologie
Sphingidae of the Western Palaearctic
Sphingidae of the Eastern Palaearctic

Butterfly Farms:
Butterfly and Orchid Garden (NZ)
Australian Butterfly Sanctuary (AU)
La Serre aux Papillons (FR)
Butterfly Creek (NZ)
Wildlife Sydney (AU)

Others:
Fauna Europaea
Lepidoptera Dissection Group
Database of Insects and their Food Plants
Database of the World's Lepidopteran Hostplants