- Beginner's Lithuanian (Dambriūnas, Klimas & Schmalstieg) - Very good textbook with stress marks on all Lithuanian text.
- Po truputį (Ramonienė & Vilkienė, 2008) - Standard Lithuanian textbook (+ exercise book). However, all content is in Lithuanian, so it's more suited for use with a teacher.
- Colloquial and Teach Yourself are both written by Ramonienė as well, so they're probably also quite good.
- Praktinė lietuvių kalbos gramatika (Ramonienė & Pribušauskaitė, 2008) - Excellent grammar targeted at learners of Lithuanian. Clear layout and lots of example sentences. Also available in English as Practical Grammar of Lithuanian.
Good dictionaries always contain stress/accentuation information.
- Lietuvių kalbos žodynas - THE Dictionary of Lithuanian (Wikipedia)
- Dabartinės lietuvių kalbos žodynas - Dictionary of Modern Lithuanian
- Sinonimų žodynas - Synonym Dictionary
- Etimologinis žodynas - Etymological Dictionary
- Wiktionary - 8th largest Wiktionary with 600k+ entries! Useful because it lists inflected forms.
- Lietuvių kalbos rašybos ir kirčiavimo žodynėlis [paper] - Pocket dictionary with spelling and especially stress/accentuation information. Highly recommended if you only need that.
- Mokomasis lietuvių kalbos žodynas [paper] - Learner's dictionary with simple explanations and example sentences.
There is rarely more than one bilingual paper dictionary available per language, so you don't really have a choice. Again, good dictionaries always contain stress/accentuation information, but the bilinguals often don't have them.
- dict.com - No stress information! They offer 30 languages in all combinations, so individual dictionaries are not optimised. However, every word comes with lots of useful collocations/examples. Nice interface.
Websites and Online Courses
- Bliu Bliu - For many languages, but they're based in Lithuania, so have lots of material for it, even for total beginners.
- debeselis.net - 196 Lithuanian lessons and a forum for learners.
- Lithuanian Out Loud - Podcast (discontinued) with 289 episodes and notes.
- oneness.vu.lt - Short 10 lesson course.
- University of Texas EIEOL - Early Indo-European Online series. Intro to the Baltic family through original texts from a Indo-European linguistics perspective.
- Cooljugator - Conjugator for 4400+ verbs
- VDU Accentuator - Adds stress markers to a text
- VDU Morphological Analyzer
- VDU Machine Translation - English > Lithuanian
- Tilde Machine Translation - Russian <> Lithuanian <> English
Let me know if you know other good resources or if you have any questions on Lithuanian!