We've obsessively combed through various listings of zoos online, animal-related associations and societies, travel guides, chamber of commerce materials, books, and straightforward internet searching...among many, many other sources.
Click here for just a few of the sources we've used that deserve a mention along the way.

AZA (Association of Zoos and Aquariums, mostly US)
CAZA (Canadian Association of Zoos and Aquariums)
ARAZPA (Australasian Regional Association of Zoological Parks and Aquaria, mostly Australia/New Zealand)
ARAZPA-QLD (ARAZPA-Queensland, formerly Queensland Wildlife Parks Association)
PAAZAB (African Association of Zoos and Aquaria)
AMACZOOA (Asociacion Mesoamericana y del Caribe de Zoologicos y Acuarios, Latin America/Caribbean)
FUNPZA (National Foundation of Zoological Parks and Aquaria, Venezuela)
FUNDAZOO (Fundacion Pro Zoologicos, Costa Rica)
ACOPAZOA (Asociacion Colombiana de Parques Zoologicos y Acuarios, Colombia)
ALPZA (Asociacion Latinoamericana de Parques Zoologicos y Acuarios, Central/South America)
SAZA/SDF (Swedish Zoo Association)
UIZA (Unione Italiana Zoo ed Acquari, Italy)
AZCARM (Asociación de Zoológicos, Criaderos y Acuarios de México)
DAZA (Danish Association of Zoos and Aquaria)
OZO (Osterreichische Zoo Organisation, Austria)
SEAZA (South-East Asian Zoo Association)
SAZARC (South Asian Zoo Association for Regional Cooperation)
ZPO (Zoological Park Association, Thailand)
JAZA/JAZGA (Japanese Association of Zoos and Aquariums)
SZB (Sociedade de Zoologicos do Brasil)
FVS (Fundacion Vida Silvestre, Argentina)
MAZPA (Malaysian Association of Zoological Parks and Aquaria
CZA (Central Zoo Authority, India)
EARAZA (Eurasian Regional Association of Zoos and Aquariums, mostly Russian)
AIZA (Iberian Association of Zoos and Aquariums, mostly Spain)
ANPZ (Association Nationale des Parcs Zoologiques, France)
BIAZA (British and Irish Association of Zoos and Aquariums)
ZOOSCHWEIZ (Swiss)
SNDPZ (Syndicat National des Directeurs de Parcs Zoologiques, France)
NVD (Nederlandse Vereniging van Dierentuinen, Netherlands)
UCSZ (Union of Czech and Slovak Zoos)
VDZ (Verband Deutscher Zoodirektoren, Germany)
MASZ (Magyar Allatkertek Szovetsegenek, Hungary)
DTG (Deutsche Tierpark Gesellschaft, Germany)
RDPOZA (Rada Dyrektorow Polskich Ogrodow Zoologicznych i Akwariow, Poland)
AMMPA (Alliance of Marine Mammal Parks and Aquariums)
EAZA (European Association of Zoos and Aquaria)
UCA (Union des Conservateurs d'Aquarium, France)
DWV (Deutscher Wildgehege Verband, Germany)
WAZA (World Association of Zoos and Aquariums)
EUAC (European Union of Aquarium Curators)
ISIS (International Species Information System)
IBAMA (Brazilian Institute of Environment and Renewable Natural Resources)
ZAA/ZAOA (Zoological Association of America - smaller zoos, mostly)
IZY (International Zoo Yearbook)
ASA (American Sanctuary Association)
TAOS (The Association of Sanctuaries)
cIMEC (Institute for Cultural Memory, Romania)
DEFRA (Department for Environment, Food and Rural Affairs, United Kingdom)
IPAN (Israeli Parks Authority)
CAZG (Chinese Association of Zoological Gardens)
USDA (US Department of Agriculture)
CMAG (New Zealand Conservation Management Group)
...and many, many more sources both online and offline ranging from government inventories to personal word of mouth

We're a little ridiculous, to be honest. After finding listings, we cross-check every possible animal location with local chambers, people who have visited or live nearby, and other reliable sources just to make sure the zoo exists. We fumble our way through websites in any number of languages (some of which we can read, some of which we can maneuver through, some of which we learn how to navigate schematically to get the information we want). Then, we track down information on its address, contact info, and what it's got inside. If the zoo is in a fairly developed nation, we can often find the address pretty easily, but we tend to zoom in with satellite maps just to be sure we pinpoint the exact spots. For less-developed nations, many hours have been spent studying local handdrawn maps (often passed online), consulting with regional authorities, and again studying satellite maps to pinpoint just the right spots if at all possible, even if an address doesn't actually exist. Whenever possible, we're also busily filling in gaps in our information if we think it will help our users.

Well, we've got to try and pay the server/hosting costs, mainly. However, the ads that are on the site we attempt to target toward things that would actually be interesting (books and DVDs related to animals on Amazon) or useful (Expedia deals) for people looking at our specific corner of the internet.

There are plenty of animal-rights groups out there that claim any captivity of an animal to be inhumane - their hearts are certainly in the right place, and the argument isn't entirely without merit. Our view is a little different though - certainly, there are exploitative, dirty, possibly cruel roadside zoos and such all over the world - those ones aren't good. However, most zoos and animal parks do their best to take care of their animals and keep the animals happy. In most developed and developing countries, there are fairly stringent standards that keep the exhibitors honest about their animal care as well (for example, India embarked on a program banning exploitative roadside zoos that existed only for entertainment and profit, rescuing and redistributing their animals to zoos with conservation and education programs). Maybe more importantly though, zoos provide a place for animals to act as ambassadors for their own species. People can learn about animals and muster up some care for conservation without coming near any actual animals, but it's when a kid gets to see a live animal in person (especially the exotic ones that they wouldn't have a chance to see in the wild) that the desire to conserve a species, to try and stem habitat destruction, etc really kicks in. Real conservation only comes from education and awareness. It may have been Jane Goodall (but we're not sure) who said something along these lines: "We will only save what we can help, we will only help if we care, we will only care if we understand".

We're going to be a little biased here (we live in Seattle), but our favorite is probably the Woodland Park Zoo. It's got a great balance of quantity and quality, basically - not as many animals as say, the San Diego Zoo, but they've got more room in Seattle. More naturalistic exhibits keep the animals particularly content and purring. Education programs all over the place, from a docent letting kids touch feathers to a Maasai tribesman telling folk stories and cultural norms of Kenya to schoolchildren. That, and one of us spent some time running observations of their little elephant Hansa (RIP), a wonderful little being if ever there was one.

Hmm...that's a tougher one. There are at least a few though. The Malayan tapir is an awesome creature - it has elements of deer, pigs, massive girth, and a prehensile snout to boot - it just looks like a fun creature to laze around with (which it really likes to do). There's a Bactrian camel in Edmonton that's particularly assured of his own sexiness, especially while he drools prodigiously. Otherwise, we tend to spend inordinate amounts of time hanging around with or near rodents - the capybara is fun to watch, and we find ourselves spending a lot of time with surprisingly friendly colonies of ground squirrels nearly everywhere we travel (and in one instance, a particularly friendly pika that hung around for some photo taking).