If the modem is really 56k and you have no desire to keep it, you might try selling it on eBay; internal 56k modems for pre-B&W G3 Macs are relatively rare. Somebody out there may be in need of a CS II 56k modem for their old box... I may have one of these at most in a beige G3, the rest are 28.8 or 33.6, though of course I don't use dialup anymore (except when I use my 540c as a fax machine).
As for the rest of it, I can't think of anything I'd do with it. I'd probably keep it for parts - you never know when you may need a spare drive, or power supply (if you can get it out of there, haha). The motherboard is also interchangeable with a number of models if fitted with a different rear plate and PCI riser (6360 and 5400-series), plus more if the power system is modified (6200/5200, maybe the 630).
As for the rest of it, I can't think of anything I'd do with it. I'd probably keep it for parts - you never know when you may need a spare drive, or power supply (if you can get it out of there, haha). The motherboard is also interchangeable with a number of models if fitted with a different rear plate and PCI riser (6360 and 5400-series), plus more if the power system is modified (6200/5200, maybe the 630).