The software used for the previous version of Chemdex packed in completely following a server update and so the update considered for summer 2009, which is not completed, is here now. The good news is the links get checked routinely now and consequently the link fail rate of some 25% on the old system will be well under 5% or so and must continue at that level. The dreadful news is most of the links are not until now in the system, however will come into view gradually in the next few weeks.
Confidently the new system (the wonderful open-source Drupal) will do a lot of the renewing, so we all get the advantage. Maintaining web site links up to date is difficult for any listing site, as you may have marked on this and other chemistry directories.