Slate has a really cool interactive animation that compares the speeds of some of the most famous ships in the 'verse.
When characters need to get from Point A to Point B with a speed that seems to defy existing rules, science fiction invents wormholes or slipstreams or other anomalies [...]
It’s a little odd that a genre about science, the field of precision, can be so imprecise. The truth is that spaceships almost always fly at the speed of the plot. But, for those who refuse to accept that, this is a definitive guide to ship speeds, based on highly scientific computer simulations and highly unscientific speculation.
I love that they included the Heart of Gold and its improbability drive.