I can't take credit for the post below as it comes from a very reputable source:
What I can say is I've used many of these tools and it's a great post that has all the links together, enjoy and thank you Duncan Parry from Search Engine Watch.
For those new to Search Marketing, below is an excerpt from the blog post...
Duncan Parry, April 20, 2012
Here are some really useful tools, some of which you will use every day, if you aren't already. Exercise some critical judgment though: a tool is only as good as it's data – so take a moment to check if the data is believable, and to think about other sources you can cross reference against.
One tool I come back to again and again is StatsCounter – there's data on the market shares of search engines, browser versions, computer, and mobile hardware and operating systems here for most countries. Whilst it's always sensible to compare two sources of this data, this is always where I start.
It always seems confusing that there are two Google tools showing search trends – Insights and Trends with the later linking to the other with the text; "Explore advanced features with Google Insights for Search". I keep expecting Trends to be closed down, but it soldiers on.
Both offer a quick way to view search trends over time by country run comparisons. Trends will also show data for 5 URLs, if they have received enough traffic to register. As well as analysing seasonality, they can be used to look at cause and effect (e.g., recession and unemployment searches rising as concerns about the economy grew in 2008 in the UK, prompting an increase in insomnia searches).
Google's DoubleClick Ad Planner show visitor levels and demographic data for sites drawn from visits to them using data from Google's own servers, a partnership with comScore and XYZ. It's perfect for profiling individual sites or, when planning a display campaign, drilling down by country, age group, interest etc. and finding a list of sites that fit your target audiences – and then filtering down to those that are in the Google Display Network and can be targeted using AdWords. It's a useful tool for benchmarking against competitors, too.
Everybody should already know this one – it's the pre-eminent source of keyword data. Data can be viewed at a national level, with mobile search volumes split off separately. Login for the ability to download to CSV, or to add them directly to AdWords.
Less well known are the Placement and Contextual tools available from this URL. The placement tool will, based on keywords, URLs, a category or combination of these, suggest sites within the Google Display Network to place ads on. The contextual tool will, based on the keywords you input, suggest further keywords to add to GDN campaigns.
Remember the power of Yandex and Badiu in Russia and China, with 63 and 78 percent market share respectively. Yandex's keyword tool covers Russia, the rest of the CIS and international traffic, showing the keywords you enter and related keywords with "Display" volumes.
Baidu has a keyword tool that only PPC advertisers can access, but they also offer an open trends and keyword tool called Baidu Index and there's a good explanation of it in English, and a list of other Chinese tools on the ChineseSEOShifu blog.
A Swiss Army Knife of free keyword tools – one to clean up keyword lists copied off webpages or from other sources by removing numbers, punctuation and words you don't want (e.g. "free"); another tool to generate all the variations of two lists of words and one to generate typos/misspellings of keywords.
A free Excel Plugin that brings in keyword data including volumes, additional keywords and other data from MSN AdCentre.
Find more keywords using Google Autocomplete and other sources. It's a quick way of understanding the universe of searches around word or phrase to find negative or positive keywords.
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