To a degree, yes; if you're logged in on one tab, and you visit a site on another tab that has any sort of Google stuff on it (which could mean a major product like Youtube, Blogger, or Picasa, or tiny/hidden stuff like Google Analytics, a Google AdSense ad, etc.), Google will know that you were there, and will associate that information with your profile.

They've tracked us for a long time -- boatloads of people are tracking us, it's amazing -- but connecting it specifically to your Google profile is new, and they're dropping the "silos" that they used to hold information in to create an even better picture of who everyone was. It used to be that your Youtube viewing habits were separate from your Picasa photo albums were separate from your search queries; now all of those things are being brought together, along with everything else Google can find out about you.

If you install Ghostery in your browser, that's going to help a lot, right there; it will stop Google from being able to see what pages you visit, because it will block all the AdSense and whatnot items from reporting your visit.