I know you can import members by using the built in import function, but that uses XML. Who keeps their data in XML...?  

There's the CSV to XML converter, but its hardly client-friendly.

Are there any alternative methods to import members?

A client of mine takes down member details manually at their store, and they want to upload them in bulk on a semi-regular basis.  

Ideally I'd like the client to just have to upload a CSV (in a format we can define).