One of the simplest to use and most affordable tools is SEMrush.

SEMRush is competitor research keyword tool with a regularly updated database of over 35 million of the most expensive keywords used to drive traffic to websites through Google Adwords and Google's organic search results. You can use SEMRush to identify organic search and AdWords opportunities, as well as seeing which keywords are driving the most traffic to your competitors.

Here is a list of some of SEMRush's key features:

• Identify which organic keywords are driving the most traffic to your competitors
• Identify which AdWords keywords are driving the most traffic to your competitors
• Identify a website's top organic search competitors
• Identify a sites top AdWords competitors
• View a website's unique Google AdWords ad copy
• Identify sites that buy ads for relevant keywords
• Identify potential sites to advertise on
• Identify the top ranking sites for specified keywords
• Identify related keyword opportunities

The organic and AdWords keywords reports allow you to analyze data for keywords, entire domains and specific URLs. Inputting a domain name or URL gives you an overall Google traffic summary for that site as well as a list of the top search queries it's ranking for within the top 20 Google search results. Inputting a keyword gives you a summary of how much traffic you might expect to receive for a specific keyword, a list of the top search phrases related to it, and the top 20 organic search and AdWords competitors.

Domain Organic Keywords Report

In this report you get a list of keywords where the site ranks within the top 20 organic search results in Google, and these related keyword details:

• Site's Google ranking for each keyword at time of data collection
• Average number of exact match queries for each key phrase in your local / chosen version of Google
• Average cost-per-click (CPC) of an AdWords ad for each search query
• Landing page URL that's displayed in the top 20 Google search results for the key word
• Estimated percentage of traffic the site receives from Google for each key phrase compared with all other referring keyphrases
• Estimated cost% ratio
• Competition of advertisers using AdWords for each search term
• Number of search results returned by Google for each key phrase
• Search query trend over the last 12 months

I absolutely love the domain and URL reports because I'm primarily an organic search engine optimizer and they help me quickly identify all of the top keywords my competitors are ranking for and opportunities I'm currently missing. If you're an AdWords expert, the AdWords Keyword and URL Reports are equally as helpful to the Organic Keywords Reports since they are nearly identical and show which Google AdWords keywords are sending the most traffic to your competitors.

Top Domain Competitors in Organic Search Results

This report gives you a list of sites that rank for the highest number of common keywords within the top 20 organic search results of Google.

For each website listed in this report, here is the associated information that is calculated and displayed in each column:

• Total number of common keywords between the sites within the top 20 Google results
• Number of keywords each site ranks for within the top 20 Google search results
• Estimated traffic each website receives for search queries it shows up for within the top 20 organic search results
• Estimated cost to purchase the same number of visitors
• Number of keyword queries the site shows up for in AdWords

This tool is great for helping you identify who your top competitors are and then digging into which keywords are sending them the most organic search traffic from Google.

Google AdWords Competitor Report

This report is very similar to the Organic Search Competitors report, but displays your top AdWords competitors.

SEMRush Keyword Report

The SEMRush keyword report is helpful for identifying the potential value of any keyword by showing you the average CPC, advertiser competition ratio, average search volume and the total number results returned.

In addition, the keyword report calculates a list of the top related phrases that might be of interest to you, as well as the top organic and AdWords competitors.

Other Reports

A few of the remaining major reports include:

• Google AdWords Ad Text Report - shows a list of your competitors' Google AdWords ads
• Potential Ad Buyers - gives you a list of sites that buy ads for relevant keywords
• Potential Ad Sellers - show top sites in Google organic results for your AdWords keywords

• Exportable reports - export to Excel, CSV
• Firefox add-on
• Order customizable reports
• API access

SEMRush plans starts at $49/mo, compared to SpyFu at $79/mo, KeywordSpy(promo code) at $89.95/mo and Compete at $199/mo.

None of the above keyword analysis services are exactly alike, so it's a good idea to research them all to see which tool is the best match for your specific needs.

Just in case you're wondering; the major difference between using a tool like SEMRush and Market Samurai(promo code) for keyword research is that SEMRush identifies your top competitors for you by scraping the web, sorting that information in a database, calculating it, and making recommendations based on their own unique algorithm. Market Samurai's keyword tool is simply an advanced interface to Google's AdWords Keyword Tool and Traffic Estimator, that makes calculations on the fly and does not maintain a database of the top Google Keywords and search rankings. Market Samurai does a great job too, but it requires you to do more manual work when identifying your top competitors and keywords. It's a good alternate if you don't have the budget for SEMRush or another keyword spy tool.

PROS: Overall I think SEMRush is a great keyword research tool for analyzing your competitors search traffic and quickly identifying new opportunities in Google. I really like the layout of the site, navigation is straightforward and the reports are well organized. The PRO pricing is very good - it is the cheapest of their top competitors, but doesn't include some of the advanced features a few of the other keyword tools do. Features such as: AdWords ad history reports, referring websites, affiliate ID tracking and email alerts.

CONS: I don't really have any complaints about the site overall. However, there are a few details that are a bit confusing. "Phrase Match" reports apparently return "Exact Match" keywords from Google's Keyword Tool, so the name of the report is a bit misleading. Also, it was difficult to understand how they are getting their estimated traffic volumes for keywords. Most of the keyword traffic volumes were somewhat close to the number I got when querying Google's Keyword Tool directly, however some numbers didn't make any sense to me at all. But that could just be a misunderstanding on my part, and not an actual statistical issue.

SEMRush is definitely a helpful tool for spying on your competitors and finding profitable new keyword opportunities.

So…What do you think about SEMRush?