Automatic updates started rolling out mid-day but if you have your network or desktop set to manually update, these are significant updates (including continued support of XP).
Most can also be found (along with a complete .iso image) at the Microsoft Download Center.
In other Microsoft news ... .NET 4.0 and Windows 7 continue with .... Visual Studio 2010 !
looking ahead (now) In concert with Tech Ed Barcelona, a CTP (Community Technology Preview) has been launched for Visual Studio 2010 along with a new website. (Note: CTP's are pre-release software and shouldn't be installed on a mission-critical computer).
Visual Studio 2010 is set to succeed Visual Studio 2008.
The CTP can be downloaded here.
edited 9:15 PM ET