Google Reader is one of the most popular RSS feed reader service. RSSToGo brings Google Reader to Windows Phone 7. RSSToGo is a fast, fully-featured and highly customizable Google Reader client that stays perfect sync with Google and presents RSS stories in a clean interface.

Features;

• Two-way syncing with your Google Reader feeds, folders, starred items, shared items and even read articles.
• Able to star/unstar, share/unshare, mark read/unread any article, even when offline
• Able to mark all items as read for any RSS subscription.
• Able to show only feeds/folders with unread items.
• Supports sharing on Email, Twitter, Google Reader
• Supports saving to Instapaper, Read It Later.
• Supports feed management – add/delete/rename subscriptions and folders, even when offline
• Able to search and subscribe to new feeds by keyword
• Use in-built browser for full articles
• Able to display mobile-friendly page using Google mobilizer or Instapaper mobilizer
• Supports sorting by newest first, or oldest first.
• Supports sorting by feed, or by date.
• Lots of other features like rotation lock, landscape view, font size and much more.

There is both free version as well as paid version. The free version is fully functional without the image caching feature.