To market our properties to other agents we:
Prepare a virtual tour and post it to our Facebook fan page and agent pages
Send an e-mail flyer to all agents in the immediate area (by zip code list)
Hold a broker open week two of the listing and have a catered luncheon for other agents
Place flyers at the office where our co-workers can see them
Place property information on our in-house TV that is in the lobby at the office.
It's common to reach out to other agents who have similar listings and let them know about it.
Per your earlier question, the most effective way to get agents to know about your property is by marketing to buyers. Your buyer is on the web looking for the best homes in their price range. Their buyer agents are doing the same thing. So as your listing looks great on the web, your buyer - and their agents - will also see it.
Hope that helps. Good luck.