Here are articles to discuss the issue of whether the Nephilim are some angel/Man Hybrid or humans:

TheFreedThinker:

Who Are the Nephilim?

Triablogue:

What are demons?

Heiser’s methodology

Enoch

Gen 6 & 1 Enoch

The Nephilim

Wayward angels

Giants In the Land

Blasphemous warrior cultures

New frontiers in exobiology

Were the Canaanites Nephilim?

Is Gen 6:1-4 about ETs?

Randy angels

Quest for the Nephilim