AQAlib
Symbol library of various boats, yachts, ships and other marine craft in DWG format. AutoCAD & IntelliCAD.
AZCAD - http://www.dbm.com.au/azcad/

Architectual Details
3000 high quality construction details in DWG, DWF, PDF and hardd copy formats covering civil, landscape, architectural, structural, mehcanical, plumbing, electrical, ADA. Suitable for use with AutoCAD, AutoCAD LT, ArchiCAD and similar products.
Architectural Details, Inc.

Autodesk Symbols 2000
More than 12,000 predrawn standard symbols that enables you to design and draft quickly for many different industries within AutoCAD LT and AutoCAD. Architectural, Electrical, Mechanical
Autodesk, Inc - http://www.autodesk.com/

AutoSYMBOL/Resource
AutoCAD symbols library for the mining, gas and timber industries.
RockWare Incorporated

Bldg Design & Const Series
Architectural design, quantity takeoffs, estimating, landscaping and structural analysis. Facilities for animated walkthroughs.
Eagle Point Software

BlockPRO
The total block management and insertion system for AutoCAD users.
JOSCO Software

Cadcells
2D and 3D cell libraries, custom line styles, and custom user interfaces for Microstation J and v8 users. Over 11,700 cells, 80 custom lines styles, and discipline sspecific menu-driven interfaces to help you navigate it all.
CADcells.com

CadPLUS ObjectEngine ™
Manages objects, symbol libraries, layers and supergroups in AutoCAD for enterprise-wide consistency and ease-of-use.
CadPLUS Products Co

CARlib
Symbol library of 2D cars, trucks, etc for AutoCAD.
AZCAD - http://www.dbm.com.au/azcad/

CheapWare Volume One
Limited Edition for use with DataCAD includes, standard and residential details, graphic symbols, drawing templates, utility macros, line types, hatch patterns and fonts.
DataCAD LLC