Ramjets are a favorite of sci-fi authors. Scoop up material as you travel, use it for fuel. Cuts down on the weight of the vehicle, so that it can travel faster, nearly the speed of light. One new addition is the ion drive Deep Space 1 was launched in 1998 and uses this technology. The spacecraft slowly accelerates so that the longer it travels, the faster it goes.
Interstellar travel is hard.
They travel at the speed of light, and can penetrate dust and gas clouds easily. Try to send messages to sun-like stars in hopes that a civilization has developed there. Can also see if anyone's trying to contact us, too. Probably something near the 21 cm line of atomic hydrogen, since any civilization that had developed astronomy would be observing there. Program runs during the idle time on your computer and searches through a batch of radio signals to look for certain things.