Over the past three years I've tried Duolingo and Busuu but not for long, they didn't suit me, too simple and not enough return for the time involved.

I started Rosetta Stone at level 2 out of 5 three years ago and completed the course, with very long gaps, early this year. It was really useful as a place to spend time with the language in a constructive way. The Studio Sessions were very useful to practise spoken French. The course is a lot cheaper than taking a weekly language teacher.

I've tried lots of other language apps and only a few have proven to be really useful to me:

Flash card apps like Flashcards and Quizlet (the online management system for Flashcards, but it also has its own app). You can download other people's topic lists. Flashcards and Quizlet were useful during my two A level years just completed, to revise vocab to fill time e.g. while waiting somewhere. But I found my own vocab book and topic-specific paper vocab lists much more productive for learning. I would try but generally failed the 20 words by heart a day maxim.

Newspaper app: I use Le Monde online (left of centre. Le Figaro is right of centre). Will prob give the latter a try next. It get the App as well, plus options such as my daily headline App, favourite topics App. Useful French exposure, even just skimming the headlines.

Podcasts I haven't started yet in French, but I often listen to live French radio on TuneIn Radio app. With Sonos wireless speakers you can beam it to any room in the house. I guess French podcasts would be useful in the car and while travelling.

I don't use translation apps as I find the quality awful.

I sometimes use Forvo online to check pronunciation http://fr.forvo.com/search-fr/vais/

Dictionary: I have sworn by Oxford Hatchett's French Dictionary App and online, which is my fifth limb. Expensive to buy but over three years has outlasted the iPhone.Very fast online search function within an entry by just keying Find Cmd/F. Useful audio for the words and even for phrases.

I use Skype online to talk in French with an American lady I met on a Rosetta Studio session. I use WhatsApp for French convo specifically with a few friends who are learners.

I use Verb2Verb App to check conjugation. Also Vatefaireconjuguer.com online http://www.vatefaireconjuguer.com/search?verb=savoir

I'm starting to use the French dictionary Antidote more,available to download. It includes the online and App versions. Check out the incorporated illustrated dictionary to learn words around a theme e.g. if you need to kill time. I find the dictionary and all the other functions, synonymes, antonymes, conjugation, much better laid out and easier to use for me than Le Grand Robert online, which has a trial version.

BonPatron App checks text message French spelling but not grammar. Copy and paste the text into BP.

Language checking: Antidote checks my French emails automatically before they're sent, for spelling and grammar. It explains what's odd, points out alternative spellings/meanings, and gives suggestions. It checks French postings online when I highlight them and click the Check tick on my desktop (see screen shot link, above right).

So my top Apps / online aids: Oxford Hatchett's, Antidote, Verb2Verb, Le Monde, TuneIn Radio on wifi using Sonos.

Off-topic, the  élan Grammar Workbook covers all French AS and A2-level grammar, so up to international B2 level. Just exercises with the answer booklet.

I look forward to seeing other people's favourites!