I am thinking about launching wide nessus scans (in the "IP range" sense) against exploits present in metasploit. The idea is to limit the number of plugins so that that the scan finishes in a reasonable time. (As a side note nessus 5.0 comes with a set of filters which allow to chose for instance "critical" vulnerabilities but, this is unfathomable to me, it is not possible to save such a configuration, ie. you have to do this manually before each scan if you want to catch the newest vulnerabilities)
This would be in essence an exercise to match the relevant plugins in nessus with the current vulnerability list in metasploit. I know it is possible to do the reverse (import into metasploit the results of nessus scans).