Warp space

A rather nebulous feature of the StarCraft universe, warp space is the series's answer to the issue of "faster than light" travel, ensuring that travel can be made between planets and systems without having to wait extended periods of time or suffer the effects of near light travel (eg time dilution). Because each race seems to undertake interstellar travel differently, it's best to group them in different sections;

Terran
Terrans developed second generation warp engines in the 23rd century, which allowed travel to the Koprulu Sector. Although the specifics of such travel are vague, there are a few indications as to its nature;

-Warp travel appears to carry great hazard, considering that if co-ordinates aren't plotted correctly, a ship's crew can end up dead and/or so far from their intended location that they can never get back (as stated in 'Firstborn).

-It takes a battlecruiser a few hours to charge up its engines for a jump, which can presumably take it furthur than smaller ships ('Queen of Blades').

-Terran ships can't jump within a planet's atmosphere; passangers must be shuttled up to ships waiting in orbit ('Nova').

It's possibly that cybernetic hibernation is used on long journeys, as it was on the original supercarriers.

Zerg
The ability of the zerg to travel through warp space was originally courtesy of the Overmind, using its psychic energy to open a passage into warp space (cinematics depict it as a circular purple gateway). The zerg are then carried off a planet into the gateway, where they emerge at their destination. It is implied that this is highly accurate ('Queen of Blades').

With Kerrigan now ruling the zerg, it's speculative as to whether this technique can still be used. It is possible that she has turned to other methods of interstellar travel, as implied by the Behemoths in 'Shadow of the Xel'naga' and the orbital space platform(s) she has. However, the technique may indeed still be avaliable, as indicated in the intro of StarCraft: Ghost.

Protoss
The protoss seem to employ warp space in a similar manner to terrans, albeit on a far more controlled level, namely in the form of warp gates, gateways, etc. These have the added bonus of being able to work on the surface of a planet. However, it appears that their larger ships (eg carriers) are able of making independent jumps (as evidenced by the cinematic when they return to Aiur).