Best tactic for redirecting .html / .php to / when transitioning static site to WP?

I'm sure lots of folks here move clients from static sites or sites that use .php / .html or similar to WP and need to make sure they use the proper redirects so that indexed pages will be redirected to new WP version ending without .php or .html to prevent a loss of rankings.

Any know of any good .htaccess redirects to accomplish this for .php and .html in MU? I've tried a few I've googled to no avail....

Any feedback on how you to this is appreciated!