The 英辞郎 dictionary powered by SPACE ALC is a godsend for Japanese learners everywhere. At first, I was floored by the edict dictionary presented by Jim Breen’s WWWJDIC and its superiority to any printed Japanese/English dictionaries you can find in American bookstores. But, I have to admit, 英辞郎 is even more amazing mostly because the WWWJDIC does not have a English to Japanese dictionary. 英辞郎 is the only dictionary I know of that can give you a clue on how to take something you want to say in English and translate it to Japanese. You can enter English phrases and have a good chance at getting some suggestions for the Japanese. Unless you have a bilingual speaker around you can ask, this is the only tool I know of that can do this.

For instance, lets say you wanted to say, “They crowded into the train,” but were not sure how to say “crowded into” in Japanese. You know 「込んでいる」 means something is crowded but you’re not sure how to use that for crowding into something. If you search on 英辞郎 for “crowded into”, you get these following helpful suggestions.

# crowded into a room
《be ～》部屋に溢｛あふ｝れる
# crowded into a small area
狭い場所｛ばしょ｝になだれ込む
# crowded into a small room
《be ～》（大勢｛おおぜい｝の人が）狭い部屋｛へや｝に押し込められる

Now you can use these suggestions and google around to see which one most closely matches what you want to say.

Yet another example. I was wondering how to say my ears popped as I was riding an elevator. I tried a couple combinations like “ears pop” and hit pay dirt when I searched for “ear popped”. I got the following:

My ear popped.
気圧で耳がへんだ。

I don’t know why 「へん」 is in hiragana but I’m guessing it’s 「変」. Now, I can deduce that in Japanese, you can say your ears feel strange for changing altitudes and that there probably is no exact equivalent for the English “ear popping” phrase. Without 英辞郎, there’s really no way to look up this type of information without having a bilingual speaker handy. (Which I think is rare for most people.)

Even something as simple as trying to find out how to say “Big Dipper” in Japanese can be a major headache without this dictionary. The WWWJDIC returns no search results because it only searches the definitions of Japanese words (and poorly, I might add). With 英辞郎, you just pop in “big dipper” and there you go.

Big Dipper
【名】 《米》北斗七星

I’m surprised that this site is supposed to be for Japanese people because I think it’s far more useful to English-speaking people learning Japanese.