If you use bit-bang mode in the FT245, you can wire DB7-DB0 directly to the IN8-IN1 pins of the ULN2803 driver chip.
If you hook up an external microcontroller to the FT245, you can do even more (more channels, more features). You would use the FT245 as if it were a serial port and transfer data in/out using the FIFO control signals. Read through the FT245 datasheet to see how the FIFO control signals work and for some simple examples of interfacing to a microcontroller. This will require you to write some code in the microcontroller to fetch data from the FIFO and write it to the outputs connected to the ULN2803 driver. This also gives you the ability to add some inputs on your microcontroller and push the data back up to your application running on the PC.