SP1 for SharePoint 2010 was released on the 28th – you can get all of the details here from the product team: Service Pack 1 for SharePoint 2010 Products is Now Available for Download.
Note that they strongly recommend you also download and install the June CU as it has some important security patches which did not make it into the Service Pack: http://support.microsoft.com/kb/2536599
Here’s a spreadsheet that lists the changes that are part of SP1 which did not come through the Cumulative Updates – http://download.microsoft.com/download/B/0/D/B0D1540B-6CF6-4674-9C8E-7A45FD91C163/Microsoft%20SharePoint%202010%20and%20Office%20servers%20Service%20Pack%201%20Changes.xlsx – here’s the list of all the server service packs – http://support.microsoft.com/kb/2510766 – and Office client apps
(e.g. Excel, SharePoint Designer, etc) – http://support.microsoft.com/kb/2510690