You should find http://www.cypress.com/?rID=43046 useful
CY7C68013A is the low power version of FX2 and currently in production.
FX2LP is a generic USB device so you should be able to get it to work with any generic USB driver. It should be able to work with libusb as well.
FX2LP requires a firmware because it is very flexible. That is one big reason why FX2LP is popular.
Please have a look at the application note I pointed you to for a firmware which you can use as starting point.
http://www.cypress.com/?rID=38232 is the technical reference manual. You should find this as well useful.
Thank you for your reply. The documents you referred me to indeed appear to be what I am after. A quick look at the documents shows some topics I am unfamiliar with -- for example at first glance it appears I will be responsible for producing a timing diagram. (With theFTDI FT245RL FIFO device, the manufacturer gave me the timing diagram to be used for the FPGA interface).
Thank you again, and I look forward to jumping into the Cypress pool with all of you!