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You can look for a robot or a controller that can hookup to your Parallel port and write some cool key handlers to control them. You can also intercept the BIOS calls like Int13 for Disk and write some disk mirroring tools, RAID drivers etc. You can hookup some transducers like Temp/vibration/pressure etc and do some data acquisition.
Would be great if its something useful for anyone.
You've familiarized yourself with low level operation of computers. Being able to read assembly may help you understand how your compiler behaves.
The rest may call some criticism, because it reflects a polarized view. One day after a one woeful embedded project, my mentor told me: "If anyone working for you writes in assembly, fire him to keep your own job." I agree with him. From a programmatic standpoint, writing in assembly is too troublesome.