Recently, I helped develop a site in PHP and had to write a script to output some user-supplied data in PDF.Being so used to Perl's CPAN, I naturally thought I would be able to find some sort of PHP module to do it. So I googled... I found two but you need to buy a commerical license to use them (http://www.php.net/manual/en/ref.pdf.php and http://www.php.net/manual/en/ref.cpdf.php). Not that appealing... So I googled more and found a few others but they were all over the place - nothing like a repository site to host them. I downloaded three (I think) and eventually got one to work.
And I suppose it wouldn't be easy to find support on the module's usage or to report bugs because of the lack of a central repository.
That brings me to CPAN.
I did a search and easily found a module that converts a document to a PDF format http://search.cpan.org/dist/HTML-HTMLDoc/lib/HTML/HTMLDoc.pm.
And that brings me to the point: I almost took CPAN for granted but I shall from now on be grateful it's there.