General Civil Engeering Sites
Civilnet - Similar to Civildesk. Has search tools but not as structured or selective.
Civil & Structural Engineering ResourceWeb
iCivilEngineer.com - directory of internet resources for civil engineering.
Construction IT Resources - database of resources for civil engineering and construction.
Engineering Software Center - your ultimate web resources for civil engineering software. Browsing or searching the Software Database is just a click away. You can also locate a company by visiting our Company Database.

GIS
GIS.com -  is a portal to GIS information on the Web and was created by ESRI, a GIS software developer.
GISLinx - This site has been compiled to provide GIS users with a quick and easy source of information on a variety of issues. With over 1,700 links, GISLinx provides an invaluable resource for all your GIS needs.

Projects
CivilProjects.com - This site, containing RFPs and RFQs will help you find the work your company is looking for.

Calculators
Unit Conversion
Unit Conversion Calculator - An excellent site for quickly and easily converting almost any kind of unit to something more useful. Metric to Imperial or Imperial to Imperial conversion available.
Unit Conversion Calculator II - Science, Currency and Unit Conversion Calculators
Hydraulic
On Line Hydraulic Calculator - Pipe flow, Open Channel Flow, Hydrology, Groundwater and Flow Measurement.  This site includes most every equation you will ever need and more besides!
Simple Hydraulic and Seismic Calculator - Easy to use water, wastewater, stormwater and seismic calculator.
Construction
Concrete Materials Calculator - The Concrete Calculators help you to estimate three significant measurements: 1. Concrete Volume: volume for a pour or placement   2. Block Wall: volume of concrete needed to fill a block.  3. Column: volume need to fill a column.
Concrete, AC, Unit Conversion Calculators
Mathematical
Standard - Science, Currency and Unit Conversion Calculators
RPN - (Reverse Polish Notation) Calculator

Project Management - Online Collaboration
Cephren - Cephren's online workplace, designed specifically for the construction industry, addresses your collaboration, project management and procurement needs throughout the design-to-build process.
Buzzsaw - ProjectPoint, Buzzsaw.com’s project-hosting service, is a centralized project workspace on the Web. It provides your team a single place to access vital project files and information — anywhere, anytime.
Bidcom - Bidcom's integrated environment and successful business process approach improves efficiency and captures best practices. Bidcom helps companies manage projects, portfolios and the entire supply chain.
Viecon - provides a real-time, interactive environment for comprehensive, project life cycle management of all the tasks and documents associated with a project. In use, you can create and manage projects with a comprehensive suite of scheduling, tracking, meeting, and calendar-based software.
ProjectQuest - ProjectQuest is an Internet based project collaboration system specifically designed to solve the real world problem of having multiple companies in different locations working on a project.
Prolog Project Pack - Introducing the Meridian Project Pack, the AEC industry’s most complete knowledge management system. Use the Project Pack to manage your projects from a corporate and collaborative perspective.

Resources
Acronym Finder - Yes, it does now what PVC and VCP stand for!
Infoplease - News, weather, atlas, almanacs, dictionary and encyclopedia.
Topozone - The TopoZone is the Web's center for topographic map users and outdoor recreation enthusiasts. They have worked with the USGS to create the Web's first interactive topo map of the entire United States. If you're looking for maps that don't leave big blank spaces between the highways, welcome!
Miriam-Webster Dictionary and Thesaurus - Need I say more?

Specifications
CSI - The Construction Specifications Institute.
ASTM - Documents available online for fee.