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Here's a delta-V map of the solar system: http://i.imgur.com/SqdzxzF.png

That seems like a orbit/landing chart. Doesn't seem accurate for head-on collisions. Or am I reading it wrong?

As a counter example, someone mentioned nearly leaving and then cheaply coming back directly into the sun.

Interesting! I would have never guessed that starting from Earth, getting to Mars is harder (by about 5%) than escaping the Solar system.

Well, there's "I want to match Mars' orbit around the Sun, so I can orbit the planet," and then there's "I want to intersect Mars' orbit just as the planet is passing through so I smack into its surface and leave a big crater."

The latter takes a lot less delta v, but it has its drawbacks. Leaving the solar system, you don't have to budget for that rendezvous.

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