Really they're buying adspace and traffic. So look for them to buy any high traffic website with innovative ideas/features. I'm sure they'd love to buy ebay or amazon, but the price tag may be too hefty. They'd love to get their hands on craigslist too, but that won't happen since they refuse to sellout.
I think I see technorati or digg as more likely target. They will need social bookmark to complement their search engine somehow
I'm not sure but most likely Google will buy something that will quadruple there income. Google has also turned to advertising via TV so let's see how big this will go.
Hmmm. I don't think they need to buy anything they do a pretty good job of creating there own sites, I'm sure they could make a site like Ebay and gather a large following, or create a Social Gathering site like Myspace.