Send it to me for free at your expense and I'll find a use for it.
Seriously though - read the stickies and other threads here or just Google and you'll soon find out what your old Xbox is capable of doing once modded. You'll also find out how to do it too.
In short: if you're not interested in playing Xbox games any more the most obvious alternative use is for emulators and/or as a multi-purpose media centre using XBMC (Xbox Media Centre).
But getting it modded either via chip or softmodding of one sort or another is the essential first step. Assuming you have a TV with the appropriate connections I'd also recommend you buy a Xbox Component cable too if you don't have one already.