A report on Bink.nu this afternoon – Windows XP Service Pack 2 build 2180 was declared ready for release to manufacturing (RTM) on Wednesday and sent for manufacturing (CD production) on Thursday.
Bink.nu / Windows XP Service Pack 2 build 2180 Released To Manufacturing
Also this afternoon, a forum posting on Neowin includes comment with a date listing of when SP2 would be available in different countries worldwide, beginning on 25 August.
Neowin / Order Windows XP Service Pack 2 on CD
See also Microsoft Windows XP SP2 official site.