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There is this http://www.shellblack.com/data/create-import-file-accounts-and-contacts/ which is great, but it's just NOT enough data!.
This is a nice resource for sample data sets
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https://mehulharry.wordpress.com/2012/02/21/free-data-sets-northwind-alternatives/
The master of all sample databases however is Northwind!
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https://raw.githubusercontent.com/tmcnab/northwind-mongo/master/northwind.csv
I ended up using this one http://timecenter.cs.aau.dk/software.htm and downloading the employeeTemporarlDataSet.zip and extracting some of the sample data for use in my Excel Power Query talk
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In Salesforce land there is Universal Containers which is used in Training, and to great effect on AutomationChampion blog for his business use-cases, and I did not know about the Warehousing App, so I will have to try that one out too.
Other Data
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Phone Numbers
Australian fictional phone numbers can be found at https://www.acma.gov.au/choose-your-phone-number
ABN
And you can test if an ABN is valid http://www.mathgen.ch/codes/abn.html#:~:text=If%20you%20don't%20have,ABN%2053%20004%20085%20616.
TFN
Some valid TFNs are here https://support.yourpayroll.com.au/hc/en-au/articles/200077535-Special-Tax-File-Numbers
To Test a TFN go here http://www.mathgen.ch/codes/tfn.html