While I was developing my looping embedded Picasa slideshow, I was also searching for alternative slideshow viewers. I don't care too much about branding that appears in many slideshow services and gadgets. Then from Google Sites forum I found (nickname) prac's RSS slideshow gadget in this thread. Tried it, and it works very well in Blogger. Thank you prac, your gadgets are great.
I use the No Border version like this:
<iframe allowtransparency="true" frameborder="0" scrolling="no" width="600" height="420" src="http://www.gmodules.com/gadgets/ifr?url=https://googledrive.com/host/0B4yfJJJSNrfubzJEUkxIYm1PcHM/picasa-slideshow-simple-nb.xml&up_CCOL=%23FFFFFF&up_SCOL=%23FFFFFF&up_PWH=560&up_PHT=420&up_DTime=3000&up_TTime=400&up_CLP=Yes&up_FEED=http://picasaweb.google.com/data/feed/base/user/mspotilas.fi/albumid/5650715941079457233?alt=rss&kind=photo&hl=en_US"><a href="http://picasaweb.google.com/mspotilas.fi/KevatKesa?authuser=0&feat=directlink#slideshow">Gallery</a></iframe>
<!-- Gadget Google - Diaporama Picasa Albums Web - http://www.liens-du-vin.ch/picasa-gadget-script.htm -->
Red parts you want to change, they are the Picasa web album RSS feed and Picasa web album (#slideshow) url, in case iframe is not supported. You must change all & characters to & in the feed url (but not in album url)! You can get the links from Picasa Web albums, from right side bar "Link to this album" (add #slideshow to it to make a slideshow link) and "RSS" (the feed). And remember to change those &:s in the RSS feed url.
Green parts you may want to change: dimensions, background colors, slide time, transition time, and link pictures to gallery or not. I use white background, 3 second slide time, 400 millisecond transition time, link pictures (up_CLP) to Picasa web album. More of the parameters here (in French).
You can see the above code embedded here in action: