Windows Phone 7, the alternative mobile OS that Microsoft has been working hard to get right, is due for its first big update this fall. Already, information about what to expect from Windows Phone 7.5, codenamed "Mango," is leaking like a low-rent faucet. Here are the juiciest details so far.

Messaging: Mango's native messaging client is said to be integrated with Facebook Chat and AIM, allowing you to chat on those services from one hub. Group messaging is also said to be included, allowing you to create group contacts that include multiple friends.

Audio and image scanning with Bing: Like Shazam, the new Windows Phone will let you identify a song that's playing using Bing Audio. You will also be able to use your camera to scan images, QR codes, bar codes and other visual data via Bing.

Visual Voicemail: Mango will finally introduce visual voicemail navigation a la iOS and Android.

Speech-to-Text: Talk to your Windows Phone 7.5 and it can create and send an SMS message of what you said.

Turn by Turn Navigation: Using Bing Maps.

Super Fast IE9 Mobile Browser: In a demo at the MIX11 conference earlier this month, the new hardware accelerated IE9 mobile left Safari Mobile and the Android browser in the dust.

Multitasking and Fast-App Switching: Windows Phone 7 will let even third party apps run in the background and allow seamless switching between active apps.

Expect the first batch of WP7 branded Nokia phones to be unveiled around the time Mango ships later this fall. It'll be interesting to see if Microsoft gets the newly acquired Skype to join the fun around then as well.

[WinRumors]