Our Mobile App of the Day is GroupMe for Windows Phone.
GroupMe is the best way to chat with everyone you know. It's absolutely free, whether you're talking to a group of friends, or texting with one person. Best of all, it works on nearly every phone, via push or SMS. With GroupMe, it's easy to reach anyone, anytime, anywhere.
On GroupMe, you can catch up with your family, get a group together for a night out, coordinate with co-workers, or just gossip with a few of your closest friends. Think about it like your own private Twitter, just for the people you really know. Or like a faster, better reply-all email.
No matter how you think about it, "you won't know how you lived without it once you give it a shot." -Gizmodo
Now a part of the Skype family.
-Start groups with the people already in your contacts...no need to remember usernames or PINs.
-Whenever you or anyone else in the group sends a message, everyone receives it. The conversation starts instantly.
-The app uses your data connection by default, but when you have a poor connection, you can switch to receiving messages via SMS. You'll never miss a message!
-Chat online when you don't have your phone nearby at http://groupme.com
-Share photos inline-take them on-the-go or choose from ones you've already taken.
-Send a direct message to anyone who has the GroupMe app for free.
Connect the app just once, and we'll keep you up to date with notifications. No need to log in every day...it just works.
-Pin groups to start
-Live tile notifications
-Fast app switching
You can grab GroupMe from the Windows Marketplace directly from your device, or here.