RSS feeds: How to reformat/rewrite/restyle? Using views? e.g. convert youtube text list of videos into thumbnails? How can a RSS feed be reformatted/rewritten/restyled to be more useful?

For example Youtube RSS feeds from the video uploads of a youtube user appear as a plain text list by default. 

Are there drupal module(s) or a solution out there that parses this content to be able to transform it into something more useful? E.g. in the case of youtube, make it show the list as thumbnail stills of the videos uploaded.
Yes Views will be the perfect module choice for you, there are many ways to tweak the output with Views &amp; it has built in Feeds support.  Google about drupal views rss feeds, you'll find a ton of info.  When you install views there is an example rss feed view you can enable and take a look at to see how its done.  As for the thumbnails if your using emfield you should have the option to display thumbnail when tweaking the field output from within the View.

Good luck!