■ USEFUL SOFTWARE
Rikaisama
http://rikaisama.sourceforge.net/
A pop-up dictionary for Firefox that shows readings and definitions when you hover over words. Rikaisama is a fork of Rikaichan that has among other new features added EPWING support, so you can use proper dictionaries for your lazy lookups.
Rikaikun
https://chrome.google.com/webstore/detail/jipdnfibhldikgcjhfnomkfpcebammhp
Rikaichan clone for Chrome. It works really badly and is a poor man's alternative to the Firefox extension, sadly.
Anki
http://ankisrs.net/
Flash card program mainly useful for vocab and kanji repetition. Can sync decks and stats between computers and your phone, utilizing a clever algorithm for spaced repetition, helping you study efficiently.
AnkiDroid
https://play.google.com/store/apps/details?id=com.ichi2.anki
Third party free software implementation of the Anki system for Android. Allows synchronization with the PC software.
EBWin
http://www31.ocn.ne.jp/~h_ishida/EBPocket.html#download_win
The best EPWING dictionary viewer for Windows, allowing you to to cross-dict lookups using Kenkyusha, Kojien and friends.
DroidWing
https://play.google.com/store/apps/details?id=com.aokabi.android.droidwingfree
Another solid EPWING viewer, but for Android.
■ WEB-BASED DICTIONARIES
ALC
http://www.alc.co.jp/
Offers a web interface to the Eijirou dictionary, made for use in translation work.
kotobank
http://kotobank.jp/
Pretty good for J-J lookups. J-E/E-J definitions from Progressive.
Tangorin
http://tangorin.com/
The best interface to Jimu Buuriinu-sama's EDICT, which is a mess, so don't keep relying on this if you want to get serious with your studies.
weblio 類語辞典
http://thesaurus.weblio.jp/
It's an extensive thesaurus.
(If you want the best J-E/E-J dictionary, get an EPWING copy of Kenkyusha. Add Kojien for J-J lookups and you've got complete protection.)
■ MEDIA
D-Addicts
http://d-addicts.com/forum/torrents.php
It's a horrible community, but it's THE go-to for drama series. Many variety shows turn up there as well. (Japanese subtitles are available here: http://jpsubbers.x10.mx/Japanese-Subtitles/)
Jコミ
http://www.j-comi.jp/
An ad-supported site offering DRM-free comics that have gone out of cirulation in print. Lots of various genres and completely legal, it is a fantastic source of reading material for learners.
JPopsuki
http://jpopsuki.eu/
It's a private music tracker with an extensive selection of just about everything.
KeyHoleTV
http://www.v2p.jp/video/english/
An application that lets you stream live TV in shit quality.
Tokyo Toshokan
https://www.tokyotosho.info/
anime anime anime anime anime (Japanese subtitles are available here: http://kitsunekko.net/dirlist.php?dir=subtitles/japanese)
■ OTHER RESOURCES
/a/'s Daily Japanese Thread
https://boards.4chan.org/a/catalog#s=daily+japanese
Recurring thread for beginners mostly focused on learning Japanese to be able to read manga and watch anime. Their OP contains huge amounts of links and book downloads, so it might be worth checking out if you're just starting out.
/int/'s 日本語スレッド
https://boards.4chan.org/int/catalog#s=日本語
A cultural exchange hub of sorts, where Japanese and international posters meet to banter about whatever they feel like. Lots of shitposting, lots of fun.
Lang-8
http://lang-8.com/
Language exchange website powered by its users. Sign up and write some entries about any topic of your liking, and native speakers come by to correct your mistakes. Just don't be an ass about it; go correct their attempts as well.