Yes, you can filter by "entry-level" on job-boards, but you have to do that for every job board. There is not one source for specifically "entry-level" positions.
This website seems to be combining ziprecruiter and neuvoo results into one. It seems to just search for "entry level", "grad", "internship" and "entry level developer" at those two websites and present the results. While passing your IP, geolocation, user agent and a bunch of other stuff to them to get location specific results.