Your options are to export records to a text format such as merge, Tab or CSV. This exports the found set, so you may need to isolate the desired records in a found set before exporting. You can then specify which fields will be exported, but the choice will be the same fields for each exported records.
Or you can use Export Field Contents to export the contents of a single field, but there's no built in ability to merge the data into a single file from multiple exports so you'd need to combine the data in a single text field prior to using this method.
Both of these options can be done manually or in scripts.