Well that depends on the type of Nokia phones you want to be flashing. I say this because if you need it for Windows devices, there are 2 official available:
Lumia Software Recovery Tool for phones running Windows 7 and previous...
Windows Phone Recovery tool for all phones running Windows 8 and 8.1.
There are some notable free softwares you can harvest from the internet for other Nokia phones, just google or bing that specific phrase and probably the first page of the search has the most trusted softwares.
All the best.