I still remember the way my science teacher explained a hypothetical warp drive (like how it is in Star Trek). He took a black towel, representing space, and laid it flat on a table. He set down a miniature model of the Enterprise on one end of the towel, then accordion-folded the towel up so that the other end was close to the ship. He moved the Enterprise over to that end of the towel, and unfolded it so that it was flat again. The Enterprise was now on the other end of the table.

An overly simplified visualization, but it really illustrated the idea to my ten year old brain how space-time could hypothetically be bent to make fast interstellar travel a possibility. Also it made me realize that warp speed on the Enterprise wasn't just a super powerful rocket or something.