Free web resources of CAD blocks

There are many sites on the Internet which offer free download of CAD blocks and symbols. Some of them are well organized, some are just a heap of DWG files, some have only simple 2D symbols, some are specialized on 3D models, paramtric libraries or AutoCAD dynamic blocks. Some are specialized to architecture, HVAC or electrical, some have mapping symbols, some have only mechanical libraries and standard parts. Even more and more manufacturers offer free CAD blocks of their products on their web sites.

Such web libraries can help CAD users to add quickly the required product, entourage or symbol to their drawings and 3D CAD models.

If you know or run a usefull free site containing blocks and families in DWG, DXF, RFA, IPT or SAT format, let me know - so I can add the link to your site.