Page strength might be a better measure of a directory than pagerank. You can find a list of directories with page strength here.
9 - yahoo, dmoz 8 - uncover the net 7 - botw, site-sift, elib.org, business.com, Microsoft SBD, what u seek try not to focus only on PR
Sometimes it is worthwhile including other directories to submit to, then you will have a balanced portfolio of directory listings
You can find some PR 7 directories over here, but a good point was mentioned, use PR as a guide, but don't try to purchase PR or go into any schemes to increase your PR, Those can be very destructive things, ..