The dictionaries, after the jump.
With no further ado, in the order that I use them when looking words up:
- ALC: ALC (pronounced アルク aruku in Japanese) is my first stop among Japanese-English dictionaries. They've got great word coverage, which means they're often my last stop as well, and they've got tons of example sentences. They seem to scan the web for translated sentences and then add those to their example sentence corpus (Google their example sentences in quotes and you can often find the source). The big thing they lack is an easy way to get to the pronunciation of words (i.e., they don't include the kana for kanji words), so for that I typically turn to Goo.
- Goo: Goo also has very good coverage, but not quite as good as ALC, and they certainly don't have as many example sentences. What they do have, however, is how to pronounce words that contain kanji. Another thing I like about Goo is their incorporation of a Japanese-Japanese dictionary, which can be surprisingly helpful—if you can get through wholly Japanese definitions.
- Jim Breen's WWWJDIC: ALC and Goo are both aimed at native-Japanese speakers (although non-native speakers can easily make use of them as well), but the WWDIC is hands down the best Japanese-English dictionary aimed at non-native speakers. (For you polyglots out there, it's got dictionaries to a bunch of other languages as well, such as Spanish, French, Russian, etc.)
It's got audio samples (courtesy of JapanesePod101), the kana is always available, and it gives you easy access to example sentences. It also has a bunch of speciality dictionaries—a rare find in free format (although not totally unheard of).
It's open source, so you'll find that other dictionaries out there make use of it, my favorite of those (which I learned of from Tofugu) is Denshi Jisho (which literally means "electronic dictionary"—like those ones you can carry around). It's got exactly the same content, but the interface is nicer and it's got a nice iPhone version as well.
- Glova: Glova is basically a massive database of translated phrases and sentences. Do a query, and you get two columns, one having the hits of your search and the other the translations—and there can be pages and pages of these hits if your search term is relatively common. It lacks the typical numbered definitions and such that you'll find in most of these dictionaries, but it's great for finding multi-word phrases when ALC leaves you empty handed.
- WordReference.com: You'll find WordReference in many of my lists of favorite dictionaries, and Japanese is no exception. Although I don't find their coverage is quite as good as those listed above, they do offer plenty of phrases for many words and the forums can be a great place to find hard-to-find phrases.
- Tangorin: Tangorin is a relatively recent discovery for me. Although they don't generally have quite as many example sentences as the dictionaries above, they do seem to occasionally have some terms that I can't find elsewhere. Their real power is in all their various speciality dictionaries, but that's a topic for another post.
- Excite, Yahoo! Japan, and Infoseek: These guys are all portals that appear to have thrown in a dictionary because the others did—and it shows. Although they have solid definitions, example sentences and other features that those above have are generally lacking. As you might guess, I very rarely need to use these dictionaries and they typically just collect dust in my bookmarks, especially since they are about as good as the Japanese-English dictionary that comes with my Mac.
This post was updated on October 5, 2009, to include Glova, Tangorin, and a reference to the Japanese-English dictionary that comes with Mac OS X.