There are plenty of RSS apps available on the iTunes Store, but plenty of them are cheap and have enough problems that using them is a chore.
Reeder is perhaps one of the most stripped down, and yet powerful, RSS readers on the store. It syncs with your Google Reader account, so all of your feeds come through automatically and there’s no need to set anything else up.
All of your reading habits are synced, so if you read an item on your computer it will show up as already being read on the iPhone. You’re also able to share pieces of content on Twitter and Facebook as well.
It costs a bit more than the usual app at $3.99, but if you rely on RSS feeds there isn’t a better way to keep up-to-date.