Do you like Do-it-Yourself projects? Ever wanted to know how to make a laptop case out of old floppy disks? How about finding out how to convert your old xbox controller to use it on your computer? You can find these useful guides (and many more) at www.instructables.com

Here's a particularly good one about all the things you can do with an old computer:
http://www.instructables.com/id/Things_to_do_with_a_old_computer/

And here's another one on how to run composite video and network data through an Ethernet cable:
http://www.instructables.com/id/How_to_Run_Composite_Video_Through_an_Ethernet_Jac/

Make sure to browse though your categories of interest, you're sure to find something worth working on!