Finally it is Here
Downloads. To download an edition of SQL Server 2005, please select an edition in the Downloads box in the upper right and click Go. Although the previous June CTP version is provided for continued testing, we strongly recommend that you download and use the current September version
All four Editions are available Enterprise , Standard , Developer and WorkGroup Edition
http://www.microsoft.com/sql/2005/productinfo/ctp.mspx
Good Luck