This was based initially on the Flickr Badge Widget, but it is a lot 
more basic, and uses a <a href="http://www.plogger.org/" rel="nofollow ugc">Plogger</a> library feed 
for its source.
I wrote it because Flickr started wanting to charge me for hosting photos. I pay a few bucks a month on web hosting, and didn’t see the point in 
also paying Flickr, given that uploading via SCP is no harder than using 
jUploadr or whatever. I installed Plogger, which seems to be a 
decent bare-bones replacement.
However, the one thing I missed about Flickr was the nice WordPress 
widget that showed my photos in the sidebar of my blog. So, I scratched 
my own itch and wrote this widget. Presto – thumbnail images in the 
sidebar.
You just assign it a Plogger feed URL and it does its thing. (The GPL 
PHP RSS library lastRSS is included – which makes this widget GPL too.)
It is still very basic and needs some developer TLC to give it the 
features that Plogger deserves. Hit me up if you can help – I don’t have 
much free time, so improvements will be slow if it’s just me on my 
own.

Plogger Badge Widget

A simple widget that displays images from a Plogger feed in the sidebar.

Aaron D. Campbell

A widget that displays rotating images from a post’s gallery in the sidebar of 
your site. You just specify the post or page, and it will cycle through all the 
images from the gallery of that post or page. you can have as many of them as 
you want on your site simultaneously. Requires PHP5.
In WordPress 2.6, another plugin of mine has been included into the CORE to 
allow these to be reorder your images to make them display in whatever order you 
prefer. Until then, go get <a href="https://wordpress.org/extend/plugins/reorder-gallery/" rel="ugc">Reorder Gallery</a>!

Gallery Widget Pro

A widget that displays rotating images from a post's gallery in the sidebar of your site. Requires PHP5.

Plogger Badge Widget vs Gallery Widget Pro