Ever since Windows Phone Mango roms (the operating system’s core code) started getting around we’ve suspected sooner or later that we would hear about some of the other new features Microsoft has planned for us this fall. What goodies did we get out of WPSauce’s dive into the Windows Phone Mango Code? Multi-party conversation for Windows Live Messenger, and Xbox Live goodies galore.

From WPSauce

Hold tight, this is the big thing. First, you will be able to share your Xbox Live profile to Facebook.
In the UI file of GameRes.dll: “Play a game, and invite a friend to play it with you.” Yes, multiplayer is coming to WP7. But hold tight a bit, there’s more.
Also in the UI file of GameRes.dll: “Listen to this message on your Xbox 360”, “Read this message on your Xbox 360”. This must be more advanced cross-platforming. If you get messages through Xbox Live and feel the small screen is way too uninteresting to read on, turn to your faithful TV.
“Invite you to a voice chat”, “Invite you to an Xbox Live party!” If I fancy it right, these fragments mean that both voice chat and virtual online party are coming to WP7 also.

They’ve got an entire list of other small tidbits not mentioned until now as well.