Parsing Filemaker 6 XML into something I can use

The Filemaker XML is something I find hard to use so I'll be trying to
export to Excel, then to CSV, then parse the CSV with either Ruby's
standard libraries or with fastercsv. If you export from Filemaker
directly to CSV, it doesn't give you the column headings, hence my
exporting to Excel format first. There's another gem called csv-mapper
which I have no experience with, but it's supposed to convert CSV to
active record - exactly what I need.

It sounds like you may already have a solution but don't want to RT*M.
That being said have you considered using something like Nokogiri
(http://nokogiri.org/) to parse the XML directly? I've had great
success parsing both HTML and XML using it, in fact it seems to be the
de facto parser used in the RoR community (someone correct me if I'm
wrong on this). But the point is, Nokogiri would probably save you a
couple steps and a lot of sanity if you intend to make going between
them (Filemaker and RoR) a regular thing.