If your business has a local clientele, such as a dental practice, a computer consulting service, etc., then Local Search is critical. It is important to be registered properly with all the local search sites, such as Yelp, Google Places, Yahoo! Local, Local.com, etc., and it is also important to have clients, patients, customers, etc., submit reviews to these sites. These reviews are very influential in getting your site to rank highly in the Local Search results. I enjoy doing local search optimization, and have done it for quite a few clients.
You may have noticed "Shopping Results" when you search for a product in Google. These result from the vendors having submitted their products to Google's "Merchant Center". Yahoo has a similar feature, and there are other shopping portals to consider.
There are many things to consider, and not all apply to every site. Each project is unique. But this overview should give you a general idea of the things we might do to promote your site.