Ideas for finding your (next) dog:
Online resources make finding a dog (both) easier and time consuming. Rescues are generally pretty good at keeping their websites up to date. The same cannot be said of all dog related sites. So, before you get swallowed by all the adorable pictures of puppies, create a strategy for weeding out more reliable sources vs. the not-so-great ones.
petharbor.com is often used by local animal control. You will have to check to see if your group is on there. Once you do, it's easy to set up email alerts to let you know when they bring in the breed you are interested in. That said, IMHO, most pets are listed as the wrong breed.
akc.org has a marketplace that lists pups that are presumably purebred. As noted by another member, that doesn't mean they are reliable breeders.
basenjirescue.org (aka brat) appears to be well-respected.
Most of the other sites I found ended up being little more that a time-suck. So, other options? How about thinking "Outside the Box"?
Your area Veterinarians' would make a logical source of information (both for new litters, and possibly 'older' patients who need a home). Check with them.
How about your local Kennel Club? Why not spend a day at their next dog show? Look for your specific breed interest, and after those breeds have competed, take a moment to introduce yourself to the breeder. You never know. They might have a pup available right then! The biggest advantage is that you have probably just tapped into a huge network of respected and well known breeders. If they don't have a dog that needs a new home, they may just know someone who does.
Other local sources that might help you find a dog: Dog Day Care Facilities, Groomers, Dog Walkers, etc. You get the point. If they are in contact with pet owners, they might know someone or maybe they could act as a middleman and introduce you to the right connection. You won't know if you don't ask.
Be patient. Don't give up. Not getting the first pup you see doesn't mean that you won't find one. And don't get in such a hurry to bring a pup home that you accept one that's "better than nothing". If it doesn't feel right, it probably isn't.