As I learned in from this message on a recent discussion on the module-authors mailing list you can link to any distribution on search.cpan.org using a URL similar to this: http://search.cpan.org/dist/*
e.g. Devel-ptkdb would always link to this distribution even if new versions were uploaded or if the maintainer changed. In addition you can link to the documentation of Devel::ptkdb too without any question marks or other things that Google does not like.
This is great because if Google can index these pages and if many people will link to useful modules then Google will rank them high and other will find them too.
Great !
I am going to look around my links and will make sure all of them point to such a URL.