If you have a link or resource that belongs on this list, please post the details in a comment below.
General Ant Websites
Antbase | Good resource for taxonomic information and literature pertaining to ants.
Antweb | Hosted by the California Academy of Sciences, Antweb is the most comprehensive website for specimen images and data. There are special Introduced Ants and Port Of Entry Ants projects.
Antwiki | Wikimedia site with the following sections: Species Accounts, Behavior & Ecology, Distribution & Diversity, Ant Societies,Morphology, Anatomy & Terminology, Biochemistry, Genetics, Development & Reproduction, Human Culture & Ants, People & History of Myrmecology.
Japanese Ant Image Database | Useful site that includes images and identification resources for many of the species included in Antkey.
Myrmecos | A large and growing collection of live insect photographs taken by Alex Wild, with a special emphasis on ants. The website contains many images of species that appear in Antkey, and it is an excellent resource for observing how the species appear in the field.
Invasive Ant Websites
Emergency Response Plan for Invasive Ants in the Pacific | A detailed document explaining how to set up a system for rapidly responding to an invasive ant incursion. Includes sections on standardized surveillance protocols, collection & identification of ant specimens, supplier details for chemicals suitable for exotic ant control, and management techniques.
Landcare Research New Zealand ant page: good resource for invasive ants in general, and those affecting New Zealand in particular.
Pacific Ant Prevention Plan | A document addressing the risk invasive ant species pose to the Pacific Island region.
PIAkey | Website devoted to invasive ants of the Pacific Islands. Antkey is an update of PIAkey, and much of the information is the same, but PIAkey has useful comparison charts that have not yet been implemented in Antkey.
Invasive Species Websites
Global Invasive Species Database | Information about the ecology, distribution, impacts, management, references, links and contacts for invasive species. The website contains a number of the species included in Antkey.