I looked down the list, and eventually picked Google Maps. Not to be boring, but because I wanted, for a change, to write something that wouldn't sound like bitter grousing.
Frankly, most "Web 2.0" stuff is crap. In fact, a lot of these 2.0 things don't really feel next generation. It seems as if the 2.0 buzzword has flowed in reverse, subsuming *any website at all* that has interactive capabilities, ignoring the original 2.0 critera - which was that web apps were becoming as interactive as desktop apps.
Google Maps is one of the very few things that I've seen so far on any of these 23 thigns that I can say would actually legitimately save me time and frustration.
A lot of these 2.0 people need to go back to the school of web design.. their sites are irritating and difficult to navigate. I'm a bad customer, because I know how things *can* be: sensibly arranged and uncluttered. When I see a site that doesn't have those attributes, I bail. I don't want to spend 30 minutes clicking around in an ugly tag cloud. No, I don't want to receive your email updates. Or yours. Or yours. I almost don't want to receive any email... ever again.
Google Maps can afford to be so good - not because of who they are, but because of the information they have behind them. The majority of the other services we've looked at rely on user-made content - their entire 'Meat' is user made in a lot of cases. That means they have to bootstrap up and tie users in so that they hang around and contribute instead of wandering by and leaving nothing behind - otherwise they never grow and never get new users. Since Web 2.0 is such an attempted-moneymaker for so many people, they pull all their marketing tricks in an attempt to grab and hold you.
In summary - I love Google Maps. They don't try to own you.