Either for entering natural history competitions that require it, or simply for more accurate titles, if you've taken a great shot of an animal or plant, how do you go about identifying what the thing in your photograph actually is?
Update: Some helpful answers already, but almost all North America based - it'd be great to have some global and/or European-based resources.
I've played around with bird and insect photography and have found that (at least in north america), there are a few good sites for this:
Use Flickr
The fun of social media is crowdsourcing expertise, much as with Stack Exchange. There are a lot of species identification groups on Flickr, where people post images with helpful ID information, and others will make educated guesses or positive identifications in the comments. This should at least get you the common name of something.
As a bird photographer learning about bird identification, I'm immensely indebted to the Flickr Bird Identification Help group. You post a picture of the bird, along with geographic location (including country) and time of year, and they'll tell you what they can. You can also use the pool itself and their answers to test your own ID skillz.
There are similar identification groups, with similar submission rules to aid group members in identification, for Insect Identification and a lot of different plant identification groups.
In addition, simply tagging a photo with your best guess and mentioning in the description you don't know might just bring someone to your door to tell you. It's happened for me with a couple of thistle shots I took in the back canyons here in Southern California, and a friendly thistle aficionado in the UK took pity on me and IDed them for me. Likewise, a friendly neighborhood herpetologist told me that what I'd tentatively thought was a Pacific gopher snake, was in fact, a gorgeous newborn baby rattler.
Use Wikipedia
Once you have the common name, it's pretty easy to look up the Latin binomial (Family species) designation. The advantage to using Wikipedia vs. paper resources for this is that Wikipedia will be more likely to capture any recent changes to classifications, and with the hypertext linking, you can generally explore what the family designation means, which can help you identify at least that far on sight (e.g., for birds of prey, you can more easily tell Buteo (broad-wing hawks), Accipitridae (accipiters), and Falco (falcons) apart).
Use a Field Guide
The problem with using a field guide is that it can probably only help you so far. Especially for the rare sightings, and the more subtle distinctions between very similar-looking or wildly hybridizing species. Which is why going with someone who's experienced and knowledgeable is probably going to trump what you can figure out with a field guide as a newb. Still, a field guide will give you the basics of what lives where during which times of year, and is liable to help you quickly learn the most common and distinctive species around you.
For North American birding, the most useful guide I found was the Sibley Guide to Birds. It's a bit too big to hump into the field, but the fact that Sibley uses his own paintings, rather than photographs, is actually a plus for me, because he mostly gives you the avatar of that species with main plumage variants, so I don't too hung up or fooled by individual looks. YMMV.
Very nice question. There are some services that do "image search" by example, they can be of help.
For example I downloaded Wikipedia photo of "Empis livida" and used tineye.com image search to find similar images. This returns a list of images, some of them including the name in Latin. I am not sure how tineye image search is useful but AFAIK Google still does not have image search by example.
There are books to identify plants and animals like the "National Geographic Field Guide to the Birds of North America".
Search on Amazon for "bird identification" or "plant identification" to find some (I got no clue which ones are good, as it depends on the area where you took the picture).
In France you always can ask to a pharmacist.
If you want to learn and/or compare, some cities with big universities have botanical gardens open to the public where most of the plants are labeled with their common and latin names. Some gardens exhibit local plants, others have rich collections of overseas flora.
There is no one single answer, and it depends on how easy the organism is to distinguish.
For plants, you're best off if you have shots of the flower (count # of petals!) + leaves (alternate or opposite leaf pattern is important) and note where you take it i.e. which state and what habitat. Some plants are easy to ID, others have obscure technical characteristics, like ridges on seeds, or stem hair length. Do a search for native plant societies in your area -- many of them are starting to put up websites of local plant species.
Generally plant and animal identification (among other things, like minerals) use a dichotomous key. The key consists of a series of either or questions based on the physical properties of an item, and depending on your response you proceed to further questions until you end up with a positive identification. It's basically taxonomy's version of a choose your own adventure book.
If you perform an internet search for dichotomous key [plant/animal/whatever] [location] you should be able to find relevant material for your post-shooting identification. There are even a few phone apps now that will allow you to identify various things.
If you want to perform more identifications in the field, you could use either the aforementioned websites (assuming you get a signal)/apps or get a physical field guidebook to the area you are in. If you happen to take pictures in or near parks with visitor centers, they often have field guides to the local flora and fauna. These usually come in the form of either regional books for specific types of wildlife etc. or park-specific brochures (which may even be free). You could, of course, also purchase regional field guides online or at the local bookstore.
Also see inkista's answer on using crowd-sourced platforms to get identification help.
I've seen people post photos of various plants and animals in biology.stackexchange.com asking for help identifying them.
There must be a zillion field guides to North American birds, waterfowl, mammals, herptiles, shells and probably centipedes.
