Help me manage my bookmarks? I find myself bookmarking webpages on my MacBook often, with the intent of reading them later. The problem is that my bookmarks end up in the bookmarks bar and then are lost as new ones are bookmarked. 

I'm looking for a tool to help me organize my bookmarks so that I can write a note along with the bookmark, and perhaps store a screenshot of the page, or even the text offline.

What are my options for a MacBook running Snow Leopard?
I think you should check out instapaper which is free.  It helps you do what you want to do without dealing with bookmarks.  Here' is the description from their web site:

"Save long web pages to read later, when you have time, on your computer, iPhone, iPad, or Kindle."

I use it so I can save something on my phone and read it later from another device.