We know what you're wondering: How does adding gear to your home leave you with more space? Although each of these might take up a little extra room on the counter or in the closet, you'll end up with more living space overall thanks to the things you get to toss now that the new gear's taken their tasks.
A Digital Kitchen Scale
What you get to throw away: Measuring spoons and measuring cups.
The New York Times has a great piece on why more at-home cooks and cookbook publishers should adopt weight—not volume—as the ingredient standard. Measuring out ingredients on an accurate digital scale means everything can get measured and mixed in one bowl.
A Wet-Dry Vac
What you get to throw away: Your old vacuum and the under-the-sink-stash of clean up towels.
It's OK if you have a larger-than-you'll admit pile of junk towels collecting mildew below your sink. You need them, right? In case there's a huge spill that needs cleaning. Unless, of course, you have a high-powered wet-dry vacuum that's as capable of cleaning up the milk as it is the Cheerios.
What you get to throw away: Any file or stack of papers you've been storing for safe keeping.
It's a good idea to keep a years' worth of bank statements in case you need them to prove income or file your tax returns. It's not a good idea, however, to let all of those documents take over your home office. Get a scanner and digitize everything, then store the files on your machine... and a backup machine... and maybe somewhere secure in the cloud, too.