Ziploc Bags are Male, because they hold everything in, but you can see right through them.

Copiers are Female, because once turned off; it takes a while to warm them up again. It's an effective reproductive device if the right buttons are pushed, but can wreak havoc if the wrong buttons are pushed.

A Tire is Male, because it goes bald and it's often over-inflated.

A Hot Air Balloon is Male, because to get it to go anywhere, you have to light a fire under it, and of course, there's the hot air part.

Sponges are Female, because they're soft, squeezable and retain water.

A Web Page is Female, because it's always getting hit on.

A Subway is Male, because it uses the same old lines to pick people up.

An Hourglass is Female, because over time, the weight shifts to the bottom.

A Hammer is Male, because it hasn't changed much over the last 5,000 years, but it's handy to havearound.