If I am a green card holder who recently filed for citizenship and want to file for my husband who is out of the country, should I file his petition now or wait until I become a citizen?

Hi. You can file now and upgrade the I-130 later with your Naturalization certificate. However, it is sometimes difficult to get that Service Center to connect it to the file. If your Naturalization interview is close, I would recommend waiting and then filing.

You can file it now and then once you become a US citizen, you will need to upgrade the petition to that of a spouse of a US citizen from that of a spouse of a lawful permanent resident.  It will probably expedite the process somewhat if you file now but probably not by too much time.