http://www.dss.virginia.gov/facility/search/cc.cgi
Some providers choose to only be licensed by the county and not the state as well, so you'd need to call County inspectors directly.
Post questions about particular providers here, or possibly on your local listserv (MONA, if you are in North Arlington, for example).
I don't know what else you might need -- inspection reports, interview/visits, references.
Figure out which inspection violations matter to you. I didn't care if another child's parents didn't put down 3 emergency contact numbers. I did care if the provider had safety or general care-related violations, especially repeated ones.