This just in: trulia now has recommendations as well. My suggestion is, when you send your “congratulations on your closing” message to your client that you rotate which link you send them to recommend you or review their experience with you. I.E. Today to Mrs. Jones I will send my yelp.com profile link and tell her to please click “write a review” in the middle of the screen to write a brief testimonial of her experience working with me or just click a star rating. Next week when Dr. Brown closes I will send the email with my zillow profile link and ask that he fill out the quick star rating review. Same with linkedin and now trulia. By doing this, I maximize all resources and webpages available and further build my online presence. Plus I allow potential leads on any site to see a positive review straight from the horse’s mouth.
This just in: Trulia follows suit with Zillow and adds recommendations!
haranhomes.org 
have you tried it out? it actually is WAY MORE IMPRESSIVE than other sites because it syndicates the written recommendation to the extended network of the client who wrote the review. So it helps raise awareness of your awesome service to potential clients who are friends of someone you helped – the people who are the biggest source of referral business for you.
Your reviews on other sites can only be found if someone actually finds your profile out of the tens of thousands of agents listed. Good luck having anyone find them let alone a friend of someone who had a good experience working with you.