http://www.toddklindt.com/blog/Lists/Posts/Post.aspx?ID=164

http://technet.microsoft.com/en-us/library/ee663474(office.14).aspx

NOTE: it is also possible to upgrade from WSS 3.0 to Sharepoint 2010 Foundation with SQL Server 2008 Remote Blob Storage (RBS) ebnabled.

http://sharepointsolutions.com/sharepoint-help/blog/index.php/2009/10/externalizing-blob-storage-in-sharepoint-2010/

http://www.sharepointmadscientist.com/Lists/Posts/Post.aspx?ID=48

http://www.sharepointjoel.com/Lists/Posts/Post.aspx?ID=274

http://sharepointmetadataandclassification.typepad.com/blog/windows-server-fci/

http://blogs.techrepublic.com.com/networking/?p=1622

http://blogs.techrepublic.com.com/networking/?p=1441

(via http://blogs.msdn.com/kaevans/archive/2009/02/05/integrating-external-document-repositories-with-sharepoint-server-2007.aspx)

http://msdn.microsoft.com/en-us/library/dd440954.aspx

My friend Vincenzo made SQL Server 2008 Filestream work with Sharepoint 2007 !! (I suppose it's unsupported by MS )

http://vincy2005.spaces.live.com/blog/cns!931A97894C3E2DDE!147.entry

(via http://sharepoint.microsoft.com/blogs/mikeg/Lists/Posts/Post.aspx?List=1b3bbb8f%2D4b5a%2D4f72%2D94c4%2D94cb80bc3866&ID=1187)

http://technet.microsoft.com/en-us/office/sharepointserver/bb736212.aspx

Is the next version of Sharepoint + SQL Server 2008 going to be the real WinFS?

you get transactional (SQL Server 2008) file storage with FILESTREAM + transactional NTFS with Windows 2008 + metadata and search with Sharepoint

http://msdn2.microsoft.com/en-us/library/bb802812.aspx

(via http://blogs.msdn.com/joelo/archive/2007/11/27/database-repartitioning-with-mergecontentdbs.aspx)
http://www.toddklindt.com/blog/Lists/Posts/Post.aspx?ID=53
http://support.microsoft.com/kb/934525

http://blogs.msdn.com/mikewat/archive/2007/11/18/sharepoint-and-storage.aspx

Very vague, but it seems it will be possible to use different storage than SQL Server, probably starting with SP1. Might it be in conjunction with SQL Server 2008 Katmai?

http://support.microsoft.com/kb/938499/

Some Posts:

http://www.21apps.com/2007/06/sql-server-2008-helping-sharepoint.html

SQL Server 2008 - Helping SharePoint Scale cost effectively

(via http://blogs.msdn.com/euanga/archive/2007/06/04/sql-server-2008-formerly-codename-katmai-public-ctp-now-available.aspx)

SQL Server "Katmai" 2008 will be good to Sharepoint  !!!

Quoting from SQL Server "Katmai" 2008 White Paper:

FileStream data

The SQL Server FileStream object allows large binary data to be stored in the file system yet remain an integral part of the database with transactional consistency. This enables the scale out of large binary data to be managed by the database and yet stored on more cost-effective storage and file systems.

Sparse columns

Sparse columns allow users to store object models onto relational data without undergoing large space costs. They also allows users to build complex content management applications with the underlying database.