Trendrr was the highlight of last week's NY Tech Meetup. It's Graphing meets Social Media. Read/Write/Web has a fine post/endorsement this week:
"Trendrr currently offers up data from 17 different data sets -- and the site is always adding more. These are things like: stock charts, YouTube video plays, MySpace friends, comments, or profile views, Amazon sales rank, Google News mentions, etc. Users can also input custom data via the site's RESTful API or by hand. Users are allowed to track up to 20 data sets at a time.
Once Trendrr is tracking your data, it can then be mashed up into comparison graph. Data can be left absolute or scaled relatively, and the site supports line, area, bar, and scatter graphs. These charts can then be embedded, linked to, or exported via excel, xml, or json. Trendrr can also export data via its new simple graph syndication API."