I realised that although I didn't manage 50,000 words in one month, I have managed over 40,000 words over October and November put together. Throughout October I spent some time trying to write a diary entry everyday, mostly of odd trains of thought I was having as I was having them, even the nonsense ones, just to see how many words I would do. I'd definitely like to see if I could combine parts of the two into any sort of entertaining novelish object.
NaNoWriMo has a list of things that you can do once you've recovered from thirty days of novel writing.
December's is all about sorting out the plot arc of the novel:
The Plot Whisperer -- Plot Writing Month (December). Goal: Refine the plot arc of your first draft.
And here are some others they've listed that go on throughout the year:
There are also 24 hour and 48 hour challenges that you can take part in if you don't fancy a month of writing tonnes of words: