We all know market research is important, but some of us (like me until recently) may be unsure as to how to gather information.

Here are some ideas:
surveys
interviews
talking to customers and businesses
Checking out government census and other statistics

On the first point, I found a great site called Survery Console.
You can create your own surveys or edit pre-defined templates for a variety of businesses, then post the link to twitter, facebook, or your own website. It's free and the website address is http://www.surveyconsole.com

Another great site for getting your product (potentially) off the ground is Quirky. This is an American website which you can submit your idea to, have other members rate the product/idea and give improvement advice, and Quirky may choose it to produce. They put into production one new product every few days. It's free to register and you earn money when helping others tweak their products! http://www.quirky.com