Ok, I know I may be cheating a bit, yet there was no size/weight restriction specified, so..
A Matson container (ocean shipping box) with:
* Sacks of plant seeds and spores (food crops, nuts, conifers, hardwoods, etc).
* Frozen reproductive cells, tissue, and eggs for all human races, animals (especially domestic birds, fish, and mammals), insects and beneficial
microorganisms (bacteria cultures, fungi, mushrooms, plankton, diatoms, etc.)
* Zettabytes of data containing the complete literary, scientific, and creative works of humankind to date, including redundant
playback/retrieval/storage devices and solar power supplies.
* Bi-directional Photo/Radio communication technology and equipment to establish links with Earth at several points enroute and at destination so
those back home that were not along for the ride may share the experience in absentia.
* Official documentation from Earth governmental authorities encouraging peaceful, long-lasting treaties and agreements for scientific and cultural
exchange with all mutually-beneficially minded sentient beings encountered.
* Gifts of Hospitality for our hosts (art, embibements, etc.).
* A (*cough*) companion or two... or three...
And, in the event this pie-in-the-sky excursion goes terribly wrong;
* A poison pill just in case I end up on some lizard-head's menu
Well, THAT was fun! Now - in the words of Jean-Luc: "Make it So!"