Another close translation would actually be kind of a literal one : "d'enfer". "That was hell of a summer!" => "C'était un été d'enfer !"

I'm not sure if there is a "perfect" translation for the expression "hell of a..." in French but we sometimes use the word "sacré" to express this idea, as in: "C'est un sacré personnage !" meaning "this person has a very strong personality" When talking about women, you can also find the expression (although I personally don't like it too much): "C'est un sacré bout de femme !" which has roughly the same meaning as the previous expression.

• First, you can always translate "hell of" by "putain de", but be aware that like all expressions referencing sex it is quite VULGAR and can only be used among close friends. J'ai passé un putain d'été. C'est un putain de bon prof ! etc... • Then I agree with Victor, especially on the translation : I spent a hell of a summer --> J'ai passé un été de fou/dingue. • Another expression which come to my mind is to emphasize with "un de ces". J'ai passé un de ces étés ! (je te dis pas). C'était une de ces fêtes ! Ce type, c'est un de ces battants ! etc... [note that it is harder to find the correct adjective to work with people using this construction, while it is almost straightforward for things].