You mean how many directories are available for us to submit to? That would be impossible to answer as there are so many and I wouldnt even want to make a guess on a number.
I dont but you will find lots under this section: http://forums.digitalpoint.com/forumdisplay.php?f=65
No,submission in without pr is not wasting of time coz the directories which r pr less can accept sites quickly and increases PR.