Commercial Brokers LLC
Commercial & industrial warehouse, office space, property management, and real estate brokerage (sales, leasing, consulting) services for Washington DC, Maryland and Virginia.
http://www.commercialbrokers.com/

Global Office Search
Global Office Search is a free, international search service for businesses looking for Serviced Offices, Executive Suites and Office Business Centers.
http://www.globalofficesearch.biz

Office Finder
OfficeFinder is a resource for office space users. In addition to lots of useful information and free tools, we also have over 250 knowledgeable and experienced commercial real estate office tenant representation experts in over 300 markets.
http://www.officefinder.com/scripts/wizard.cfm?referrer=LRE

OfficeRealtors.com
We make finding office space easy! Utilizing our up to the minute commercial database, we start by providing you with information on any building in Maryland, Washington, DC, or Virginia that matches your leasing requirements.
http://www.officerealtors.com/

Offices2share.com
Offices2share.com is a nationwide listing service that brings together those companies that have short-term office space with businesses and individuals seeking short-term, ready-to-move-into offices.
http://www.offices2share.com/