I can't understand why someone wouldn't want to access the entire Northern IL Multiple Listing Service (MLSNI) to be able to search for every single active listing. I guess because most sites require some kind of registration.
Maybe you're not ready to actually view homes and are just starting your search. You don't want to register with anyone because you're not at the point where you are ready to go setting up appointments to see homes.
If that's the case, then visit the Chicago area real estate MLS listings page to view a huge selection of properties without having to register. You can do a search and will get a list of properties available per your search parameters. You will be able to see a photo and a small description.
If a listing piques your interest then you can do a quick and easy registration and see multiple photos, a full description including room sizes and even a virtual tour link for the listings that have them.