What are those strange web-like things in tree branches along long island highways?

Question

There are hundreds of them. I cant tell if they're nests or webs or what. Thanks!

Answer 1

Tent caterpillars?

Answer 2

if I remember correctly and am picturing what you are describing, its a parasitic plant called "dodder".  There are a number of parasitic vine plants through out the world.  the link below describes some of them.

Hope I got it correct.... and it answers your question.