While you easily add website links to Google Bookmarks using the Google Toolbar in IE or Firefox, an option definitely worth considering is Yawas.
Yawas (short for Yet Another Web Annotation System) is a brand new Firefox extension that offers something extra which you may not see in existing social bookmarking add-ons.
You can highlight one or more blocks of text on a web page and they automatically get saved inside the notes field of your Google bookmarks account along with the address of that website.
The more interesting part is that when you revisit that web page in future, Yawas will automatically highlight the text portions on that web pages that you have earlier clipped to Google Bookmarks. So you immediately know about the sections that you earlier found to be interesting.