Although it’s not announced on the main site yet, most mirrors already have it: RC5 of PostgreSQL 8. With the release being planned late this week, and RC4 claimed to be the last RC before release, RC5 is a surprise. But the changelog from RC4 to RC5 lists quite a few changes/fixes, so my prediciton will be that late this week will change into early next week.
Choose one of the mirrors to download the software. It’s in the beta directory.
The Windows-installer version can also be found here.