Commons is a bit messy, since it started with a focus on archiving and sorting images more than displaying them (except insofar as they're displayed in Wikipedia articles), so it's not surprising that third-party sites are re-presenting its content. And since its point is to collect freely licensed content and promote reuse, there's nothing wrong with that. But there's a bit more focus recently on making it directly browsable.
Commons is a bit messy, since it started with a focus on archiving and sorting images more than displaying them (except insofar as they're displayed in Wikipedia articles), so it's not surprising that third-party sites are re-presenting its content. And since its point is to collect freely licensed content and promote reuse, there's nothing wrong with that. But there's a bit more focus recently on making it directly browsable.
Slideshow gadget info: http://commons.wikimedia.org/wiki/Help:Gadget-GallerySlidesh...