The UCN5821 looks like a combination of the popular 595 (serial to parallel converter) and something like a ULN2803 (high current darlington driver.) Nice chip, probably pretty useful for either small to mid-sized steppers or LED arrays on the cathodes (note: sinks current only, which means it goes in between your load device and GND...)
The DAC probably isn't very useful. It'll use a lot of pins to essentially get you behavior similar to that provided by the PWM outputs already.