Based on the IAU definition of planet there are 8 planets in our solar system. If you look at the xkcd pic there are eight planets inside the box labeled "our solar system". One is very small, mercury.
There are also about 5 additional confirmed dwarf planet in out solar system: Ceres Pluto Haumea Makemake Eris
And numerous other dwarf planets that have been spotted and are almost confirmed: Orcus – discovered on February 17, 2004. Quaoar – discovered on June 5, 2002. 2007 OR10 – discovered on July 17, 2007. Sedna - discovered on November 14, 2003.
Plus dozens more dimmer ones that have been spotted and are being vetted by the astronomical community.
There are also about 5 additional confirmed dwarf planet in out solar system:
Ceres
Pluto
Haumea
Makemake
Eris
And numerous other dwarf planets that have been spotted and are almost confirmed:
Orcus – discovered on February 17, 2004.
Quaoar – discovered on June 5, 2002.
2007 OR10 – discovered on July 17, 2007.
Sedna - discovered on November 14, 2003.
Plus dozens more dimmer ones that have been spotted and are being vetted by the astronomical community.