Do eukaryote cells contain DNA that isn't part of a chromosome or located in the mitochondria?
In plants, chloroplasts and other plastids contain DNA, but I suppose you are more interested in humans. Quoting from wikipedia,


  In many cells cytoplasmic DNA is also found, which is different from
  nuclear DNA, both in methylation levels (cytoplasmic has less), and in
  sequence. EccDNA or extrachromosomal circular DNA is present in all
  eukaryotic cells, derived from genomic DNA and consists of repetitive
  sequences of DNA found in both coding and non-coding regions of
  chromosomes. EccDNA can vary in size from less than 2000 more than
  20,000 base pairs. In animals, eccDNA molecules have been shown to
  contain repetitive sequences that are seen in satellite DNA, 5S
  ribosomal DNA and telomere DNA. The function of eccDNA has not been widely studied, but it has been proposed that the production of elements of eccDNA from genomic DNA sequences adds to the plasticity of the eukaryotic genome and can influence genome stability, cell aging and the evolution of chromosomes