Google Places is great and is the king of the search! Bing is in charge of Yahoo's search engine, so it would not matter if you made a Yahoo listing. I mean you can, you just would not have to fill both of these out, just one.
Also Yelp(believe it or not) a review site, lets you list your business free and does show up in the Search Engine Rankings.
Manta, Merchant Circle and Hot Frog are very much worth listing your business as they too will eventually get you noticed.
Fill all of these profiles to the fullest potential, include photos..GOOGLE will allow 10, I highly recommend at least five if you cannot get 10.
I highly recommend everyone get a LinkedIn account(also FREE) Find professional groups, such as on here, for every niche and connect with other professionals in your industry. Great learning and traffic getter!
Now to keep your rankings...let the real work begin.