NASA makes a new Image Of The Day available every day in their gallery,
complete with a fairly detailed description of what you see. This plugin
grabs a thumbnail of the current image along with an extract of the
accompanying description, and makes it available as a WordPress sidebar
widget. Clicking on the thumbnail will take you to the NASA Gallery where
you can view the full sized image and read the rest of the text. No
local storage is used, the image and text is fetched on every view.
A friendly user let me know that the Image Of The Day is also
available as an RSS feed. That greatly simplified this plugin and
should make it impervious to cosmetic changes at NASA. In
addition to this, the image width is now customizable. The height
is calculated per image so that it stays proportional when scaled
(down) to width.