Here's the benefits, pulled from another site. There may be more.
There is a lot of reward in reciting Surah Kahf either before the jumu'ah salaat or after it. Rasulullah (Allah bless him & give him peace) said: "The person who recites Surah Kahf on Fridays, a nur will appear for him from below the arsh as high as the skies. This light will help him in the darkness of the day of resurrection . And all the sins which he may have committed from the last Friday till this Friday will be forgiven . " (Sharh Sifrus-Sa'aadah)
The ulama have written that this Hadith refers to minor sins because major sins are not forgiven without making taubah.
related by Hakim and Bayhaqi, from Abu Sa`id (Allah be pleased with him), �Whoever recites Surat al-Kahf on Friday, light shall shine forth for him between the two Fridays.�
(a) From Abu Sa’eed al-Khudri, who said: “Whoever reads Soorat al-Kahf on the night of Jumu’ah, will have a light that will stretch between him and the Ancient House (the Ka’bah).”
(Narrated by al-Daarimi, 3407.)
(b) “Whoever reads Soorat al-Kahf on the day of Jumu’ah, will have a light that will shine from him from one Friday to the next.”
(Narrated by al-Haakim, 2/399; al-Bayhaqi, 3/249.]