Question: I'm using the Adobe CS5 suite and trying to upload all of my pictures to Facebook... and .NEF files are too large to upload, any suggestions?

Answer: 
Irfanview is free ,and does it all.

* <https://www.irfanview.com/>

Irfanview has been progressively developed over many years and is used by literally millions of people. It's free for private use - a donation is welcome but not essential.  

It does what you want and a vast amount more.

If using, be sure to install both the progam and the separately downloaded "plugins".
NEF is Nikons Raw image format, which thends to have a size over 10MB.

To display a picture on the internet, mainly embedded into a website like facebook or email, you need to use a compatible image format that is displayable by the browser (client). Most compatible image formats are JPEG, GIF and PNG.

Image sizes commonly used on the internet are below 300KB, which is a fraction of the size of a NEF.

Your NEF's will have a dpi higher that 72. For displaying images on a screen 72 dpi is sufficiant, so you might want to reduce dpi as-well, additional to scaling the image (length or height around 1000px is a good starting point).

You need to convert the NEF into a format and size explained above. As already said by others, you can use any RAW converter to do the job. I would recommend to use Nikons own software like Caputre NX, which offers batch processing, or the View NX, that most probably came with you camera and offers batch processing as-well afaik.

Just a note, be aware what you upload to the internet, especially to facebook ;-)