How do I flush the DNS cache on a OS X 10.6 machine? Trying to flush the local DNS cache. How is this done on Snow Leopard?

Using System Preferences and using the terminal?
Use

sudo dscacheutil -flushcache


or

sudo killall -HUP mDNSResponder


In 10.6 the handling of Unicast DNS is now managed by mDNSResponder - dscacheutil -flushcache now just tells mDNSResponder to restart (the second command above).