Polish server for many games, like Ludoteka or Yahoo! Games. Support for English language is provided. Many weak players, but several polish dan players also show up :) http://www.kurnik.pl/en/ (MK)
Kurnik even saves your games and emails SGF files to you. The ladder rankings are also fun to climb, as well as regular online tournaments. If you like Scrabble (Literaxx), the interface is also beautiful. (Halfling)