what will be a good tax saving device similar to PPF ?

I want suggestion for a/few tax saving scheme(s) of reputable institutions where one is required to fill up forms only ONCE.and go on with monthly / yearly subsription year after year.Also it should have least locking period.Thanks
if such schemes do not exist,then scemes with low lock in period—some real experience in mutual fund by an iiinvestor may be helpful