Using barrels to collect rainwater is a common practice here in Canada. Just put it below your eavetrough downspout.
However, most people use plastic ones, and use the wooden ones as planters.
I met the owner of a small, boutique Napa Valley winery a few weeks ago, who was lamenting that he pays $800 per barrel, uses them for 3 years (2 vintages), and then ends up cutting them in half and selling them to gardeners for $40 a half. That's quite an expense amortized into the price of the wine.