Stacks for Instapaper is being offered over at the Windows Phone 7 Marketplace for $2.99. Stacks is a Instapaper companion app for your Windows Phone that allows you to access your Instapaper account while on the go.
Instapaper is a popular web service that allows you to save web pages that you discover during the day but don't have time to read. The service saves these pages for later when you do have the time to take it all in.
Stacks allows subscribers to organize and read their bookmarks on their Windows Phone. Log in and view all your folders. Progress bars let you know what's left to read. Pick your favorite font and size, switch to Night Mode and multitask all you want: bookmarks reopen exactly where you left off!
You need a paid subscription to Instapaper to use this app. There is a free trial version available for Stacks and again, the full version runs $2.99. You can download the Windows Phone app here (opens Zune) at the Marketplace.