many of them by doing a Google search with keywords like independent filmmakers, independent film, or film production. These sites list jobs, production companies, cast and crew available, post production houses, film labs and just about anything that has to do with making movies.
You can find most of the information you need to make a low budget movie online, but if you really want to find a quality cast and crew you need to get down in the trenches where the independent filmmakers work. You need to go and meet them in person.
The best place to find potential crew members is to visit the equipment rental houses in your area. You can get their addresses by doing an Internet search using the keywords film equipment rental with the name of the nearest major city. This is where the camera people, sound people, grips and the like all go to pick