Yahoo!知恵袋 This is the Japanese equivalent of Yahoo! Answers and similar English-language sites. Very useful for finding answers to questions related to Japanese, e.g. the difference between 「分かる」, 「判る」, and 「解る」 and so on.
Tools
rikaichan - FireFox Add-on
This add-on is a dictionary from Japanese to English/German/French/Russian. You hover the mouse on top of a word, and then a popup appears.
rikaikun A Google Chrome extension supporting a pop-up English-Japanese dictionary feature similar to rikaichan.
Japanese anime transcripts on other sites
These are actual transcripts, unlike the 'subtitle transcripts' at ジブリ作品字幕COLLECTION. Some of these titles also have subtitles available on Kitsunekko, although in some cases the actual transcripts are far superior (e.g. for 桜花抄 from 5 Centimeters Per Second).
Jin-Roh: The Wolf Brigade (人狼 JIN-ROH) (the Japanese Blu-ray comes with official subtitles/日本語字幕 [which can be downloaded from Kitsunekko's collection], but this version appears to have been transcribed by a fan)
There are also lots of pages/sites that collect 名言 (memorable quotations) from anime shows. There are many Twitter bots like this too. They can often be found by googling things like "[name of anime] + セリフ" or "[name of anime] + 名言".
Miscellaneous resources
終わりの惑星【ホシ】のLove Song (lit. "Love song of an ending planet")
This isn't an anime but a ‘concept album’ produced by Jun Maeda, the creator of Air, Clannad, Angel Beats!, etc. Four out of all thirteen songs on the album are available at the official YouTube channel in the form of animated music videos with Japanese subtitles. (Starting with the first song, “Last Smile”, is highly recommended, because its subtitles are completely in sync with the music and the lyrics are easier to understand. The second song, “終わりの世界から”, also uses fairly basic vocabulary and kanji usage, but the third and fourth songs are significantly more challenging. Note that there are no English subs or translations provided for any of the songs.)
Tools
rikaichan - FireFox Add-on
This add-on is a dictionary from Japanese to English/German/French/Russian. You hover the mouse on top of a word, and then a popup appears.
A Google Chrome extension supporting a pop-up English-Japanese dictionary feature similar to rikaichan.
Japanese anime transcripts on other sites
These are actual transcripts, unlike the 'subtitle transcripts' at ジブリ作品字幕COLLECTION. Some of these titles also have subtitles available on Kitsunekko, although in some cases the actual transcripts are far superior (e.g. for 桜花抄 from 5 Centimeters Per Second).Please feel free to add more links!
See also this page.
There are also lots of pages/sites that collect 名言 (memorable quotations) from anime shows. There are many Twitter bots like this too. They can often be found by googling things like "[name of anime] + セリフ" or "[name of anime] + 名言".
Miscellaneous resources
This isn't an anime but a ‘concept album’ produced by Jun Maeda, the creator of Air, Clannad, Angel Beats!, etc. Four out of all thirteen songs on the album are available at the official YouTube channel in the form of animated music videos with Japanese subtitles. (Starting with the first song, “Last Smile”, is highly recommended, because its subtitles are completely in sync with the music and the lyrics are easier to understand. The second song, “終わりの世界から”, also uses fairly basic vocabulary and kanji usage, but the third and fourth songs are significantly more challenging. Note that there are no English subs or translations provided for any of the songs.)