Having tried some of these nice web services, I would like to run it now on my own server for obvious reasons. Even after spending considerable time, I didn´t find so much useful out there. eyeOS or other web based OS produce a large amount of overhead while allowing for only one RSS reader window at a time. From the 23 or so widget management systems the only Open Source piece that I found was Posh from Portaneo who deposited at Sourceforge. I wonder why it has only 2,095 downloads so far as all other candidates (Cesar, Viewport, MuseStorm Desktop…) are demo applications only. Widgets for Posh are quite limited so far while the (most important) RSS feed widgets already work.
More useful pages are at gnetvibes.rubyforge.org.rubyforge.org, dev.netvibes.com, reblog.org.
Addendum
Dropthings: another Open Source core engine