Listening in for "the buzz" at the Web 2.0 Summit here. A couple things I'm hearing a lot about are:
widgetization - clearly Adobe is going to capitalize this with AIR, but the idea that your web apps should be portable is full-on across the board.
open APIs - this is kind of a no-brainer with the prevalence of Facebook platform (they asked the room how many people were involved in some way with a Facebook app when Zuck was on stage and about 70% of the people in the room raised their hand!). Speakers who are not opening their platforms were being chided onstage by their interviewers (Meg Whitman from eBay for example).
presence - the concept of presence is on a lot of lips. This is what Twitter is all about. People microblogging their every move online. This sounds like a flash in the plan to grown-ups, but AOL and Microsoft are talking about it and so are a lot people here. Going to be in the Wired/Tired/Expired column soon.
Facebook - did I mention Facebook?