How would you ask? I want to ask when I can expect to hear from them, but without sounding like "hey, why haven't you gotten back to me yet?"

Beginning of next week. They likely need to still circulate reference results and make a decisions.

I went through two rounds of interviews with a job I'm really interested in and they told me that they would be calling my references. It took them a week and a half to get a hold of one of my references and they just finally spoke on Monday afternoon, which I know because my reference updated me. That means it's been almost 2 weeks at this point since they told me they were going to call my references, and two days since they finished talking to all of them.

When would you follow up for a status update?