Free info on market size, demand etc.

When writing a business plan or proposal it helps to have genuine information on the size of target market (and other statistics).

Is there any free web service that offers such data/info?

Some example questions: - size of digital photo printing market in USA - number of prints made every year...

Some info I can get through Google but would be great to know about a free service that offer the same (I know about few paid ones).