I'm using MagpieRSS to display a couple of RSS feeds in my blog sidebar. That would be a nice thing to have rolled into an easy-to-install plugin. There could be a backoffice tab (or section in the tools tab) for defining a feed and the number of items from the feed to display. This could be stored in a database table. You could have several feeds programmed in the backoffice, then call each one through a skin tag and use the params to tell it which feed you want. Maybe the number of items to be shown could also be overridded through the params in the skin. MagpieRSS has a cacheing system. I don't know how hard that would be to include with all of this.

I'm not sure how the other plugins are doing this, but it would be nice if you could select a feed in the backoffice and have it tell you exactly whay code you need to place into your skin to display the feed in the way you want.