Particularly I'm interested in mitochondria-related genetic diseases and aging. The reason is that I'm trying to figure out an use for our Ilumina sequencing machine and build a project spanning across science, healthcare and business.
if it's for human disease, try the UCSC genome browser (take care of the genome build), there are many tracks that could help you (http://genome-euro.ucsc.edu/cgi-bin/hgTracks?db=hg38&lastVirtModeType=default&lastVirtModeExtraState=&virtModeType=default&virtMode=0&nonVirtPosition=&position=chrM%3A1%2D16569&hgsid=224374244_svPcgRPFLPfGsPSPs0CWV4lWG17L). each track is associated with data downloadable by the table browser.
It's estimated that there are around 1,500 mitochondrial nuclear genes (genes incorporated into the vertebrate genome). So, to address mito aging, you'll need to look at the mtDNA and the human genome. I would suggest, along with USCS as Fred stated, is that you look at mitimap. This will give you pathogenic and phenotypic information for mtDNA. It's curated and binned nicely. As for nuclear genes associated with aging, there are a number of reviews available. You could intersect the nuclear data with the mitochondrial proteome to help narrow down your search.