I find it really almost funny how little most people know about the standard wordcount of typical novels. Even fellow writers. And yet it's important to know so that you don't under or over estimate the size of your novel and turn off agents that would otherwise be very interested in your work.
A standard 300 page adult novel is 80,000 words. Most YA novels are less.
But don't just take my word for it! While doing research on the topic yesterday (to inform fellow NaNo writers over at the FTN forum) I came across this excellent blog post which gives common ranges for most genres.
Some other numbers...
The Fellowship of the Ring - 177,000 words
A Tale of Two Cities - 135,000
Pride and Prejudice - 122,000
Twilight - 118,000
Wuthering Heights - 107,000
Harry Potter and the Sorcerer's Stone - 76,000
The Scarlet Letter - 63,000
And while I'm at it, I'll mention that as long as you are looking at proper word count, make sure you've got a properly formatted manuscript as well! Use a clear size 12 font (something like Times New Roman is best) with double spaced lines and at least a one inch margin around the entire page. Before you send your lovely work off to a publisher, do some further research into such things as where to include your name and title, line breaks, and other important details. A simple google search will bring up everything you need to know, but do read more than one article as different people will give you slightly different pieces of advice.