There are numerous aggregators around, each of which has a different take on aggregating. Most commonly there’s the business card idea (retaggr) and recently I’ve been playing with Geek chart which shows activities as a piechart.
Today’s big idea is a social network aggregator where activities are displayed on a timeline. Users should be able to show/hide different services and browse the timeline in chronological format. Also, the timeline should be able to be manipulated like Google Finance’s stock price timelines – they’re very slick indeed.