Time Series Data Library
The time series data library from Rob Hyndman has hundreds (~648+) of time-series data. It depends on what you call "demand" and what you require as a "sufficiently long period of time."
The entire dataset has been migrated to an R package called tsdl. It is also available on GitHub.
You can find descriptions of the data in the meta data.
Select examples:
"Monthly demand repair parts large/heavy equip. Iowa 1972 – 1979"
"Montly av. residential gas usage Iowa (cubic feet)*100 ’71 – ’79"
"Monthly gasoline demand Ontario gallon millions 1960 – 1975"
"Monthly sales of U.S. houses (thousands) 1965 – 1975"
"Monthly Av. residential electricity usage Iowa city 1971 – 1979"
"Monthly car sales in Quebec 1960-1968"
"Monthly U.S. housing starts (privately owned 1-family) 1965 – 1975"
"Four-weekly totals of beer shipments"
"Annual unit price of lynx pelts (Hudson’s Bay company, Canada) 1857 – 1911"
"Annual yield of straw on Broadbalk field at Rothamsted 1852-1925"
"Basic quarterly iron production in Australia: thousand tonnes. Mar 1956 – Sep 1994"
"Monthly beer production in Australia: megalitres."
"Quarterly beer production in Australia: megalitres. March 1956 – June 1994"
There is another way to see data descriptions:
The raw data is also available. If you drill down, there is a README.txt for each one (e.g. example for "monthly"). These text files are viewable on GitHub in your browser.