Language lessons
Debesėlis: A new growing website, with grammar lessons, pronunciation, phrases, vocabulary, forum and friendly people
Lituania en castellano: Lithuanian resources complete with a language course (in Spanish)
Dictionaries and phrasebooks:
Alkonas: English-Lithuanian-English dictionary online
Downloadable dictionaries in several languages
Modern Lithuanian Dictionary
Kaip tai pasakyti lietuviškai? Phrases and audio files (in Russian)*
Lingva Prismo: Phrases and audio files
Мультиязыковой проект Ильи Франка: Includes a downloadable Lithuanian-Russian-Polish phrasebook (in Russian)
Vilna.info: Finnish-Lithuanian vocabulary**

Information about Lithuanian language and its history:
Gerbkime žodį (in Lithuanian)
Lituanus: History of the language
Lietuvos.net
Virtual calendar: Etymology of names (in Lithuanian)
Lithuanian literature:
Katekizmas: Archive of Lithuanian literature
Lithuanian Classic Literature Anthology
Lithuanian tales with translations into English
Wordtheque: Lithuanian tales
Other:
English-Lithuanian Vocabulary Quizzes
* Typos:
Prašau atnešti [s]sąskaita[/s] sąskaitą.
[s]Gelbėkita[/s] Gelbėkite.
[s]Iškvieskitte[/s] Iškvieskite greitąją pagalbą.
** Typos:
Juusto = [s]suris[/s] sūris
Peruna = [s]bulve[/s] bulvė