Nottingham is full of breweries. So far, I know the following: Castle Rock, Blue Monkey, Nottingham Brewery and Navigation. If you know any other, please, send me an email telling the name and where to find a good pint of it :)
I intend to include in this list pubs in Nottingham that sells good beer not from Nottingham, such as the Junk Yard. Soon.
1) Blue Monkey
I had a really good first impression, but the last Blue Monkeys I tried were not particularly good. I plan to drink more soon and then form an opinion. Not easy to find in pubs (except by the Organ Grinder, official tap of the brewery) but available bottled.
Their stout "Twisted Genius", is common in pubs around the city and it is my standard option in pubs with nothing new to try. I recommend: not brilliant, but good and for a reasonable price.
2) Castle Rock
It can be found bottled and in some pubs in Nottingham. In my opinion, it is the easier local beer, maybe too easy, but still a good choice.
4) Nottingham Brewery
My favourite! That is why I included the map right here.
The book 1001 beers to drink before die recommends their Extra Pale Ale and so do I. Good balance in the flavour. However, my favourite is the Oatmeal Stout, only produced during winter. It is fantastic! The best stout I have ever drunk (and I really like stouts!).
The official tap is a very local and traditional pub, with kind customers and staff. According to my experience, I would say this is a very typical British pub. They do not serve food, except on Quiz nights (Thursday) when the food is free!