Wordtracker: Wordtracker is a paid web utility that gives marketers access to research information and data from multiple popular metasearch engines, like Blingo, Dogpile, Kayak, and Metacrawler. It is credited as being the most popular keyword research tool for pay per click advertising campaigns (PPC).

Part of Wordtracker's success is due to the fact that Mike and Andy Mindel, creators of the keyword research solution, first built the tool in 1998. That's before Google was out of beta and a long time before search engine optimization became the name of what would become a rapidly growing digital marketplace. Today, with eMarketer estimating web users will spend $1.5 trillion online in 2014, Wordtracker has become the foremost tool for marketers looking to get their brands in front of web surfers through PPC.

That shouldn't be read to mean that Wordtracker is a perfect marketing tool -- it's not. As aforementioned, Wordtracker does not -- cannot -- pull search data from Google and other popular search engines, especially now that Google has begun encrypting that data. In other words, Wordtracker is limited to metasearch engines. Additionally, because of the relatively small sample size the tool pulls data from, it is possible to manipulate that data.

That said, Wordtracker is the most popular keyword research tool for PPC campaigns for a reason: it's the best thing out there, save the AdWords keyword tool.