Yes indeedy, you certainly can with a can! Boost wi-fi that is, with a homemade beer can antenna. Or soda can. Doesn't make a difference (I don't think a can of tuna will do the trick, though).
Your wi-fi router -- you know, that little dojigger that sends wireless signals throughout your home or office -- is omnidirectional. That is, it's sending out its little electromagnetic waveforms every which way it can, including down into the earth, straight up to the sky and over to your neighbor's house (who loves having free access to your wi-fi, by the way).
A properly-formed, thoughtfully directed and nicely smooth aluminum reflector can help your router focus its signal strength exactly where you want it focused, leaving a much weaker signal in the areas behind the reflector.
Your friendly beer/soda can is easily snippable, lending itself to a quick, five-minute transformation into an ideal wireless booster (once it's been emptied, of course...select the beverage of your own choosing). And since the can already comes with a hole in the lid, where the pop-top used to be, you can slip your reflector right over your router's antenna and voila...a stronger wireless signal. Instant extra bars!
You know that spot in your living room where you can never get a reliable signal? Try it now! I used it on my Belkin wireless-N router and it worked like a charm.
The proper can-snipping technique is something where pictures do a better job than words, so have a look. And enjoy your new found freedom.
Need more information? Newspaper archives are one of the best online research tools.
If you're searching for information on people, try Intelius.