- Parla.cat is the best learning centre I've found so far. There are multimedia courses to take you from basic to advanced level, forums for practising with other learners and plenty of references on grammar etc.
- Catalan at the UB: Learn Catalan via Internet. A long list of resources, although some of the links are dead.
- Two websites for conjugating Catalan verbs: verbs.cat and Verbix.
- I am still searching for a good English-Catalan Kindle dictionary and translation app for Android. If anyone knows of one, please get in touch.
General language learning
- Anki spaced-repetition software is the language-learner's very best friend. If you don't use it, you should! (Thanks to Suzy Hamilton for introducing it to me.)
- LanguageTool Style and Grammar Checker — open source spelling and grammar proofing for text in over twenty languages. Catalan, German and English are among the best-supported so far.
- Lang-8: write entries in your target language and have native speakers correct them, while doing the same for learners of your native language. Ninety languages are represented on the site by now.
Non-Catalan language resources
- My favourite online dictionary is dict.cc and their Android app is also wonderfully reliable. Unfortunately, they don't have Catalan. Maybe they will soon?
- Free Kindle dictionaries for eight languages. I've used the German one and like it. No Catalan, though.
- Linguee is a helpful tool for translating phrases between five European languages (English, French, German, Portugese and Spanish).