The web makes it possible to search for documents written in every conceivable language, but what if you don't actually know the language you find that special somethin' written in? No worries—there are plenty of online translation services that can give you anything from just a good idea to a complete translation of what you're looking at. Disclaimer: None of the following language translation services can substitute for a real live human translator.
Language to language
Say you've got a block of text you need translated. Generally, the best tool for the job would be Babelfish, a simple translation service that translates something for you "from" a language "to" a language.
Google Translate can unlock blocks of text for you from language to language. You can also use it to translate an entire web page by simply entering in the URL, but this doesn't always work the way you'd like it to (they also have a language to language dictionary, as well as a way to set Google's interface in your preferred language.) There's also gTranslate, a Firefox add-on that uses the Google translation service to translate the text on the page so you don't have to visit the Google Translate site itself. Windows Live has a similar service.
One of the best (and easiest to use) language translation tools available right now is the FoxLingo add-on for Firefox. It translates web pages and block text in 45 different languages.
There's also Translate 2.0, a simple translation site that keeps a running track of your entries and offers them up in a PDF format for extra handiness.
WordReference is a set of free online translation dictionaries (French, Spanish, Italian, etc.) that offer a bit more than just straight word to word translation; you also get a spoken word demo as well as detailed etymology of the word or phrase you're trying to translate.
Specific Language Tools
There are many translation sites out there that specialise in just one or two languages, which actually makes them more useful since they tend to pick up on more language to language idiosyncrasies. Beolingus is an English/German site that offers translation services as well as definitions, synonyms, example sentences, and aural samples.
Misc. Language Tools
The Speech Accent Archive, while not strictly a translation service, does offer you the opportunity to listen to literally hundreds of languages being spoken by native speakers— a great way to see if you're saying something right or getting an ear for the language.
Anyone who's ever attempted to learn a language knows that verb conjugations can get tricky. That's where Verbix comes in handy; it's a free online verb conjugator available for dozens of languages.
If you want to read news in your language from all over the world, try Newstran, a free translator for over 10,000 global newspapers. Note: be prepared for some slow load times depending on what language you're looking for.
How about videos? dotSub is a small but growing site that offers a selection of (mostly technology-related) videos translated into a variety of other languages.
You can use the Internet Slang Translator to figure out what someone is saying to you online; for more on-the-fly translation goodness, try the Google Translate Buttons, drag and drop language functionality for your browser toolbar. In addition, if you're someone that needs language translation services frequently, you might want to check out setting up a Yahoo Pipes system to translate an RSS feed in another language.
While none of these tools can sub for a native language translator, most of us don't have the luxury of one of these folks sitting right in front of us when we need them. What's your favourite language translation tool? Let's hear in the comments.
Wendy Boswell, Lifehacker's Weekend Editor, needs to brush up on her French.