Mark O'Brien wrote a great easy read on this exact topic, it's called "A Website that Works" - http://www.newfangled.com/a_website_that_works This is the philosophy that Newfangled is built upon, so let me know if you're ever interested in partnering with us for consulting or development. Good luck!

Typically, the easiest starting place is with a focused blog that you contribute new content to frequently. The flipside would be to create one thought-provoking thought leadership piece (whitepaper, ebook, etc.) that you can use to drive traffic to and show your expertise. Another route is to purchase a highly-targeted email list of people in your target audience and use that list to push content to via email. That would be a quicker way to get a large number of eyes on your content, as opposed to (or in addition to) starting from scratch with a new blog and relying on people to find it via search. But there are some obvious pros and cons of purchasing a list. That being said, a lot of this will depend on your business and what your goals are. If you're interested in chatting about this, let me know. Newfangled (the company I work for) offers a lot of content marketing consulting, so we can likely get you moving in the right direction.

Google Analytics is the best free tool out there for this. Make sure that you are focusing your report on conversions - how many/what percentage of website visitors are taking action (filling out a form, buying a product, etc.). If you're interested in paying for help, you should check out Moz or HubSpot, but Google Analytics is your best free option for web reporting. They also provide some social reporting - which social networks are driving traffic to the site and which network referrals are leading to the most conversions. Good luck!

I also cannot speak to the legal aspect, as I am not a lawyer. However, as a web consultant, I have many clients who use similar strategies from product resellers to realtors. Real Estate has a system for this in place, the "multiple listing service" (MLS) - http://www.mls.com, which allows you to aggregate real estate data from other brokers. However, one thing to consider in this area is the effectiveness of this strategy. If you are not producing any unique content, but instead only reposting content from other sources, then the search engines could see you as a "content farm" (http://mashable.com/2011/02/25/google-content-farms/). If you want to show up in search results and bring in traffic to the site, then you will need to be producing some sort of additional unique content of value. Be that in a blog or other info added, you will need a content strategy that goes beyond reposting content from other sites, or the search engines are going to punish you accordingly.