You must visit all these sites. They can also E-mail any job vacancies directly to you for free. They too can E-mail jobs to you. The European Chemical Society is also worth a look. Either for jobs or post-Docs .
Science is pretty good too.
The Riley Guide, which is worth a look. A fairly exhaustive list of chemistry related newsgroups can be found at UCLA . The First Division. These are the big Websearchers. Particularly their Companies page.