Mashups: The next major new application development model?

Microsoft Mashup tool : http://www.popfly.ms/ (Also see silverlight framework from MS)
Yahoo Mashups : http://pipes.yahoo.com/pipes/

Excellent blog article on mashups : http://blogs.zdnet.com/Hinchcliffe/?p=106
Excellent blog on widgets : http://blogs.zdnet.com/Hinchcliffe/?p=80

Thousands of widgets you can add : http://www.widgetbox.com/