51 Pegasi
Announced in October of 1995, 51 Pegasi was the first planetary system ever discovered, done so by Michel Mayor and Didier Queroz at the Observatoire de Genève in Switzerland. 51 Pegasi contains a sun-like star orbited by a Jupiter-class planet.
Upsilon Andromedae 2
The first multiplanet system to be confirmed was Upsilon Andromedae 2, with the first of discoveries being announced in 1997 and later confirmed in 1999. Upsilon Andromedae 2 contains one Jupiter-like planet and two larger planets, while scientists have suggested the potential existence of a fourth planet.
PSR B1620-26
PSR B1620-26 is a binary star system that also was the first multistar planetary system discovered. Confirmed in 1999 and 2000 by scientific reports, this system has a single planet orbiting the two stars, a pulsar and white dwarf .
Gliese 581
Gliese 581 is a renowned planetary system for multiple reasons. It was the first planetary system discovered with an Earth-like planet (Gliese 581d) orbiting within its habitable zone. Although since then, scientists have speculated it is likely too hot to be habitable. There is another candidate for habitation also orbiting Gliese 581 called Gliese 581g that was confirmed in 2010.
Kepler 11
In 2011, NASA confirmed that they had discovered a sun-like star that was orbited by six planets. The planets, all bigger than earth, are surprisingly close to the sun, resulting in what was called by NASA as the "fullest, most compact planetary system yet discovered beyond our own."