Most star Systems (like our Solar System) are Single (research published 2006)... BUT this is because as many as 85% of the stars in our galaxy could be Red Dwarfs, and they tend to be solitary!

It's likely that most STARS are part of Binary Systems:

This Accretion Disk Binary System  is an artist's conception ( Astronomy Picture of the Day) of one type of binary star system, in which the larger of the 2 stars seems to be pulling material from the smaller star because of the larger star's greater gravity. In this case it's because the smaller star has expanded near the end of its life, and its outer atmosphere is essentially falling on to the other star. The larger star has at this point become a white dwarf, neutron star, or black hole.

Most stars are actually part of binary or multiple star systems

•   2 or more stars orbiting around each other

BUT...

• 2/3 of star Systems in our galaxy may be single systems, most of which are single Red Dwarf systems
• as many as 85% of the stars in our galaxy could be Red Dwarfs (Type M)

so

• 1/3 of star Systems in our galaxy may be multiple-star systems
• the number of stars in multiple-star systems is very large, though, so more than half of all stars in our galaxy are probably in multiple-star systems.

so

• our solar system, which is most likely a single star system (theories about an as-yet-unseen companion not withstanding) is part of the 2/3, but of course is NOT part of the 85%. Remember it is a type G2V star

• Orbiting Binary Stars animation (interactive!)

• Investigate Binary System Animations.
•  BINARY STARS   (Cornell University)
• Binary Stars (U. Oregon)

The star Mizar:...

Many stars are members of star clusters:

Gravitationally associated stars that "travel together" through space.