Interested in 'the deepest hole ever drilled'?
The answer is not simple as the research and exploration is being conducted by several different countries (and groups of countries) simultaneously and discoveries are not posted or released immediately (or completely) to the entire world.
Multi-year projects are currently still on-going in the area of deep-drilling research and exploration.
Try websearches on the following:
Wikipedia is a great starting reference, but wherever possible, you should rely on geoscience information from government agencies such as the USGS (United States Geological Survey), NOAA (National Oceanic and Atmospheric Administration), CDMG (California Division of Mines and Geology) now known as the CGS (California Geological Survey) and/or established colleges, universities and research laboratories (e.g., Scripps).