depends what you want to find out from your competitors, tell me so I can be more specific, I know of many tools.
Yes,.. I agree with T_Media Tools did't given complete report, you need to check manually also. But try this link It will provide some little bit info : * Page Size * Word Count * Image Count * Link Count * Link Popularity * Flash * Frames * Keyword Density * And More!
You can use yahoo site explorer to find backlinks, seodigger to find keywords they are getting ranked for and google trends, alexa to see traffic details.
Here are a few websites you could check out. http://www.compete.com/ http://www.quantcast.com/ and you could click here to read more about it.
I find the following tool pretty useful: http://www.linkdiagnosis.com/ It will analyze competitor's backlinks and the anchor text.
I find Micro Niche Finder to be fantastic. It gives out search count, exact phrase count, adword costs per keyword, competition out there, and tons of other stuff I haven't even used yet. It does cost some money, but if you're an investor then it might be one of the best things you use. I believe you can just go through micronichefinder.com and it will come up for you. Good luck~
On similar lines, we have a tool from Seomoz named linkscape. It would provide good info on the link structure of your competitors.
seochat is pretty useful for all type of tools. I am using seochat from past 4 years and it's good to rely upon..
Well, the most simple and yer workable option and solution is taking a look at the number of competitors websites shown on Google pages when you perform a query.