I consider the "free report" more of a proposal.
For me the report usually summarizes a fairly quick analysis I do on any client's site.
I look at the following:
-Google Analytics Data (if available)
-Top Keywords and where they currently rank for them
-General layout of webpage, content currently being published
-Backlink profile (I don't share this with them, but it gives you an idea of what you're working with).
To summarize what I look for above:
-Google Analytic's Data: Here I focus on their current incoming organic traffic, what keywords is bringing in that traffic, what pages on their site are converting the best/worse, where I can improve those statistics. Usually I plop in a few small graphs with some goals I have for them - use data from past projects to project out what you might be able to accomplish.
-Keywords: General ranking, who the main competitors are, what keywords the are focusing on vs. what I think they should focus on. How keyword dense their website is.
General Website tips: Just using my general web design knowledge I take a look at all their conversion points and offer up some nice multi-variate tests that I would consider running, as well as what changes I would propose to test out. (Drop the word multi-variate and you look like a genius in most cases

)
Content: I look at their top content pages, what kind of content they are writing, whether they maintain a blog, whether they maintain any microsites as well as how often they update.
I try to summarize all this information in less than 2-3 pages. Before I even write a proposal I also try to get the client on the phone. I make sure I'm not turning this into a "pitch" call persay, I just ask a whole ton of questions about their business. It gives me a nice idea of where their strengths lie, and what might work for them when it comes to IM.
Usually that's one of the first times they've had a web designer or SEO really eager to hear about their business and learn about what they do for a living before I give my pitch (to earn MY living).
EDIT: Rereading the threads above it looks like you are looking for a quick way to provide a free report to leads correct? My process may be a bit more indepth, but getting that "personal touch" turns more than 90% of my leads to clients. Granted I waste my time on that 10%, but you always end up learning something along the way.