The internet is a great place to get an overview of what's available in the local housing market, but it should not be your only source of information. Much of what prospective homebuyers find on the internet is old information or sketchy. Finding what you believe might be your perfect home, only then to learn that it is already sold or no longer on market, is an exercise in frustration. The www does not replace the help of a local expert.
You also should be aware that some houses are sold before being posted online, and some are never online (due to seller preference and other reasons).
In fact, the best way to start your search is to consult a tech-savvy REALTOR who can set you up for automatic emails, based on your search parameters. You will get the information much faster than trolling the internet on your own, because REALTOR-provided information comes directly from the MLS.
All other sources get the information second-hand, after it rolls out from the local MLS feed. That can take from one day to several days. Most of the second tier sites populate the information initially, but few of them UPDATE the information. MLS, however, is constantly updated.
When the REALTOR-driven search sends you an interesting property in your price range and in the geographic area where you want to live, you might also find additional photos are posted online. Many customer views from the MLS will include several photos as well as a link to additional online photos or virtual tours. In my market, extensive photo collections of current listings are posted on Houseviewonline.com and semohousehunter.com. It's very easy to look up a specific home on either site, simply by typing in the MLS number.
Of course, when you are ready to actually visit houses, you will need the help of that agent who has been feeding you up-to-the-minute information. A phone call or an email is all it takes to get started. Just let the REALTOR of your choice know what you are looking for: location, price range, number of bedrooms, and any other requirements that are important to you (basement, garage, ranch style, number of baths, school district).
That is all it takes to get a reliable, automatic stream of information in your inbox. You don't even have to meet the agent in person, though why would you NOT want to meet a wonderful agent ;-) in person. If you are in my market, drop me an email. I won't bug you--that would be a waste of my time and yours. I will, however, send you the information you have requested. In return, I hope you will call me when you are ready to buy.