You can bookmark a page by clicking the star in the location bar. Clicking on it once will save the bookmark in the "unsorted bookmarks" location, clicking on it a second time allows you to choose where to save the bookmark.

You can also use the keyboard shortcut Control+D to bookmark a site.

Yes, but I cannot access my Google Bookmarks by simply clicking on an icon and bookmarking it. I want to save a URL to a folder in my Google Bookmarks. It seems like I have to go through extra steps to save in my google bookmarks. What am I missing?

Firefox will not directly save to Google Bookmarks, an add-on like the Google Toolbar is needed.
Is the Google Toolbar even compatible with Firefox 5.0b2?

Keep on mind that Firefox 5.0 is like a month away from being released, it is still under development.

Okay, thanks. That is what I needed to know.