Windows Live Dev is a portal focused on developers and enthusiasts who want to learn the Live development platform and create mash-ups and participate in the Microsoft’s next generation web initiative. - http://dev.live.com/
So what is Windows Live Platform
Windows Live Platform enables developers and enthusiasts to easily take advantage of Microsoft web services and more quickly deliver rich, personalized web experiences across the web.
The Windows Live Platform includes the following services:
Rich Media DeliveryMicrosoft Silverlight Streaming by Windows Live offers a free streaming and application hosting solution for delivering high-quality, cross-platform, cross-browser, media-enabled rich interactive applications (RIAs).
ContactsThe Windows Live Contacts enables developers use Microsoft’s contact store to use their Windows Live Contacts with a web site. This enables a developer to build an application/website that uses (with the explicit consent of the end user) the contact information users already maintain in Windows Live. This offers the potential to add a social dimension to any website, and when coupled with presence and IM offers a rich set of potential scenarios for websites.
AuthenticationThe Windows Live ID service (formerly known as the Passport Network) is the identity and authentication system for all Microsoft online services. Currently, over 300 million users have credentials that work with Windows Live ID.
MappingThe Virtual Earth Web Service is Microsoft’s next generation mapping and location service. It deliver innovative mapping services, including bird's eye, satellite and aerial imagery, map styles and enhanced local search.
SearchThe Live Search Web Service enables developers to create applications that return results from the Windows Live Search Engine. It allows you up to 25,000 queries a day for use in both commercial and non-commercial sites to delivers search ability for a wide range of specialized search applications across a range of scenarios and industries.
Spaces/PhotosThe Windows Live Spaces control enables end users with photos in their Microsoft Spaces to enable 3rd party sites to access these photos for sharing and additional services. By enabling users to give permission to multiple sites to access their spaces photo, a user can avoid the need to upload photos to multiple sites. Users will maintain control of photos and be able to easily revoke or other limit access to their photos from 3rd party sites.