Everybody knows the crowd sourced open street map.
There are also a crowd sourced stats: numbeo. Self declaration of http://www.numbeo.com is as follows:
‘Numbeo is the biggest free database of user contributed data about cities and countries worldwide, especially living conditions: cost of living, housing indicators, health care systems, traffic, crime and pollution.’
It’s not the (harmonized) price index statistical agencies disseminate. It’s much more pragmatic and useful for detailed information about single prices at specific locations.
I didn’t compare with official indexes. To do this would be an interesting task … and a quality check.