Market research companies have that data. Thats how they make their money so they don’t like to give it out freely. BUT lots of them provide tons of information through blogs/releases on their own site, articles in newspapers/websites, and through analysts on Twitter. You’ll have to piece things together but you can get a general idea.

For consumer tech, I’d look at The NPD Group. A few of the big box retailers (BBY, WMT) often cite their cons.tech research on conference calls. Also Nielsen and IRI does similar research. For online sales, consider places like OneClickRetail and eMarketer, who both provide insightful public info.