Hi Shari
If you are looking for websites for realtors in terms of listings, Realtor.com is definitely a good choice.
In terms of information for real estate professionals, you should check out TopProducer.com. They have a lot of information about marketing and other resources for realtors who want to improve their business.
Hope this helps!

Are you referring to websites to list on ?
http://www.Trulia.com , http://www.Zillow.com , http://www.Craigslist.com , http http://:www.GoogleBase.com

Agent-2-Agent Resources ?
http://www.Activerain.com

Website Systems ?
http://www.realivent.com
Multi-User blogging websites, single property websites, agent websites and online flyers.

Joomla! is a great free resource for REALTORS. I am setting up my site on Joomla. It's easy (for nerds) to install, simple to manage, and reliable. http://www.joomla.org/

Trulia.com, realtor.com, topproducer.com. I like the real estate center website at Texas A&M. Anything with statistics, demographics, or trends. I also like igoogle with widgets as a desktop.

Check http://www.activerain.com. It is a great social network for real estate professionals, but buyers and seller are invited as well. It is a great resource for anyone interested in real estate.