Absolutely. There were a great many political parties during the Weimar Republic. Some of the more well-established ones were the Social Democratic Party (SPD) which had existed during the Kaiserreich and exists today, and the Center Party (Zentrum), a centrist/conservative party comprised of and supported mainly by Catholics. But as with many parliamentary democracies, there were many smaller parties. The most important of these was the Communist Party of Germany (KPD), which saw an explosion of support after the onset of the Great Depression just like the Nazis did. In fact, in the November 1932 election (the last free and fair election in Germany until after the war), the KPD took just under 17% of the vote, which put it in third place behind the NSDAP (Nazis) at 33% and the SPD at 20.5%. The reason this is important is because the KPD was just as openly anti-democratic as the NSDAP.

The other notable small.extreme party was the German National People's Party (DNVP)--not to be confused with the German People's Party (DVP). The DNVP was not dissimilar from the NSDAP--they were anti-democratic, reactionary, anti-semitic, and based in German nationalism and the voelkisch movement. They formed coalitions with the NSDAP, though their leaders were generally sidelined by the Nazis due to their more monarchist sensibilities, but their rhetoric was remarkably similar to that of the NSDAP but without the charismatic leader that the Nazis had in Adolf Hitler.

Most histories of the Nazi rise to power discuss the DNVP and the KPD. I know William Shirer's The Rise and Fall of the Third Reich discusses both. You'll also find some discussion of the politics of the late Weimar Republic in Ian Kershaw's two-volume biography of Hitler and a few others that have slipped my mind at the moment.