Paul, what kind of waveforms, speeds, and repeatability are you looking for? If you can handle software timing and jitter, then you could just change the digital outputs in a loop.
If you need fast, steady, repeatable pattern generation, then we offer the NI-6533 and NI-6534. The DAQPads don't currently have any support for digital pattern generation. You can get it in PCMCI format however with the NI-6533.
Hope this helps,
John Nieri
Applications Engineer
National Instruments