Case-Shiller, the most respected index of home values, just released their July report, which showed continued improvement of home values (though still down significantly from peak values).

SocketSite has an extended article describing how the report applies to the SF Metro Area: http://www.socketsite.com/archives/2009/09/july_spcaseshiller_san_francisco_msa_continues_mom_upti.html

The new Case Shiller report PDF can be found here: http://www2.standardandpoors.com/spf/pdf/index/CSHomePrice_Release_092955.pdf

Remember the C-S report covers the SF Metro AREA, not just SF, so it includes other counties with very different markets.