Social Birthday Tile uses your Facebook account to figure out which friends of yours have birthdays this week and show it on a live tile! In the app itself, you can go and post on your friend’s wall using message templates. You can see how it works on my Nokia Lumia 800.
You can also manually add your own contacts if they are not present on Facebook or if they are using privacy settings.
Social Birthday Tile is a very simple app that I find very useful. It costs 99 cents, but you can try it for free. The only limitation I see on the trial version is that a message pops up before it opens. Download it at the Windows Phone Marketplace and let us know what you think!