The new features of the Xbox Live Spring Update through the link, over 80 of them. The list is extremely long, so I'll post the highlights.
5. Introduce a group chat (4) for Private Chat and conferences through Video Chat.
8. More fields present in Personal Profile - recent achievements, interests, games, movies, links, custom section.
29. New button on Marketplace for optional dashboard features - uses Storage Device memory.
30. Option to donate Microsoft Points to anybody with a Windows Live ID.
31. Option to purchase Membership for charities (includes benefits).
32. Integrate file-sharing for selected titles on Xbox LIVE and Games for Windows - LIVE.
36. Web feeds integration - text, images, audio. Includes support for specific item codes on Marketplace.
1. Option to delete titles from gamercard with 0 gamerscore and 0 achievements (excludes some titles that will be re-added to launch another title).
2. Organize My Games at the Games Library section better (includes disc-based titles) - sort by genre, platform (Games for Windows - LIVE), percentage completion.
3. Support to display friends leaderboards for disc-based titles.
4. Show dates of an achievement unlocked when comparing.
Kotaku states this as a rumor, but other sources deem it true. I hope it is.