Back in the early 90s I designed a digital frequency synthesizer add-on to an existing product. The user could dial in frequency using thumbwheel switches almost identical to these. This system didn't have a computer, and I ended up converting the BCD digits to the binary control word needed by the synthesizer using a series of EEPROMs - one bank to do BCD to decimal, and another to do a reciprocal operation.
As for projects, how about using them to set a clock? Or build an old-fashioned front panel to a modern ARM embedded board.
-Chris