Where to find dictionaries for other languages for IntelliJ?

Current IDEA versions load dictionaries in UTF-8, you don't need to convert them to the platform encoding, ignore the iconv step below.

The dictionary can be produced using aspell for Unix/Mac OS X or under Cygwin. You need to have aspell and appropriate dictionary installed.

Here is the example for Russian dictionary I've used:

aspell --lang ru-yeyo dump master | aspell --lang ru expand | tr ' ' '\n' > russian.dic

For German it would be:

aspell --lang de_DE dump master | aspell --lang de_DE expand | tr ' ' '\n' > de.dic

This is based on all answers from here but including all the steps. I'm on Mac OS X (I think it will work on linux as well, except aspell installation) and I want the spanish dic

Only execute on terminal those lines that start with $ symbol

1. Install aspell:

   $ brew update
   $ brew install aspell
   

2. Download Aspell dic from their official repo

3. Extract tar.bz2 file

4. Go to extracted directory using terminal

   $ cd Downloads/aspell6-es-1.11-2
   

5. Compile and install dic.

   $ ./configure
   Finding Dictionary file location ... /usr/local/Cellar/aspell/0.60.6.1/lib/aspell-0.60
   Finding Data file location ... /usr/local/Cellar/aspell/0.60.6.1/lib/aspell-0.60
   $ make
   /usr/local/bin/prezip-bin -d < es.cwl | /usr/local/bin/aspell  --lang=es create master ./es.rws
   $ make install
   mkdir -p /usr/local/Cellar/aspell/0.60.6.1/lib/aspell-0.60/
   cp es.rws castellano.alias es.multi espanol.alias spanish.alias /usr/local/Cellar/aspell/0.60.6.1/lib/aspell-0.60/
   cd /usr/local/Cellar/aspell/0.60.6.1/lib/aspell-0.60/ && chmod 644 es.rws castellano.alias es.multi espanol.alias spanish.alias
   mkdir -p /usr/local/Cellar/aspell/0.60.6.1/lib/aspell-0.60/
   cp es.dat es_affix.dat /usr/local/Cellar/aspell/0.60.6.1/lib/aspell-0.60/
   cd /usr/local/Cellar/aspell/0.60.6.1/lib/aspell-0.60/ && chmod 644 es.dat es_affix.dat
   

6. Create the .dic file using:

   $ aspell -l es dump master | aspell -l es expand | tr ' ' '\n' > es.dic
   

I downloaded the ASCII spanish dictionary from this page, copied the included .dic file and it worked without any change: http://www.winedt.org/dict.html

There are many other languages.

OUTDATED: I get this info from this page (now this link is dead), who included additional details and format conversions that I didn't need: http://blog.novoj.net/2010/11/07/how-to-add-your-own-dictionary-to-intellij-idea-spellchecker/