ntpdate and xntpd would be my choices I'd say.

Ntpdate will do a one-off sync when you run it (so you can put in in the startup or cron it)

xntpd will keep you in sync with the time master by shaving a few microseconds off or adding them on until it catches up or slows down to the right time.

I use xntpd when I can as it produces smaller time shifts when correcting.