StackInbox 1.2

Checks your inbox, every 2 minutes, for new items, and when it does sets the dock badge icon to a Star
Supports Growl, get an on screen message when new items are found. You don't actually need Growl for this to work, and you can disable this in StackInbox preferences if you don't have Growl.
You can choose to have the number of unread items in the dock badge in Preferences.
Auto-refresh happens every 2 minutes.
Clicking on an item opens it your web browser (this isn't a client which you can view the site in, on a desktop the website is the best for that :))
Keeps track of unread items itself, so you don't miss a new item.