ASKING THE IMPORTANT QUESTIONS: No Fairy Tale: Will Giants Return to Usher in the Messianic Era? ( Adam Eliyahu Berkowitz, Breaking Israel News). Without endorsing this or any other eschatological scenario, I thought the mix of traditional sources cited in this essay was worth noting.
Lots more on the Zohar is here and links. The Zohar is written in the name of Rabbi Shimon bar Yochai (Shimon ben Yohai), but was composed long after his time. An excellent collection of midrashic material by Jack Collins, relating to the Flood, the watchers, and the giants, is noted here. The Midrash of Shemihazai is to be translated in the second volume of the More Old Testament Pseudepigrapha Project, along with the rest of the Book of Giants material. More on Og the giant is here and links. The Nephilim have appeared frequently in PaleoJudaica and you can find the many posts through the search engine.
I have never before seen b. Sanhedrin 97a brought into the discussion of the Nephilim and I am skeptical that "Bar Nafli" has anything to do with them. It looks to me to be a messianic title based on the phrase "the fallen booth of David" in Amos 9:11. But I am willing to hear the case made if someone wants to make it.