1 Google Analytics
Adds the Google Analytics web statistics tracking system to your website.

Provides the ability to selectively track certain user roles. Now with support for segmentation - allowing tracking of logged in visitors by user id, username, and profile fields from within Google Analytics.

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2 Node (key)Words/Meta-tags
Allows users to add meta tags, eg keywords or description.

Nodewords renamed meta tags, adds meta tag and meta keyword description which in many way has lost relevancy with most search engines but can still provide a useful description for the page and help reinforce content.

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3 Pathauto
Provides a mechanism for modules to automatically generate aliases for the content they manage.
Pathauto is a very simple module that automate path aliases turning example.com/node/1 into example.com/mypagetitle its very customizable allowing you to set paths based on date, or almost any variable. It also has a bulk update feature allowing you to update your entire site. This module is particularly useful to SEO because it adds semantic meaning to nodes based on their titles, it also is easier for a visitor to remember.

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4 RobotsTxt
Generates the robots.txt file dynamically and gives you the chance to edit it, on a per-site basis, from the web UI.
Use this module when you are running multiple Drupal sites from a single code base (multisite) and you need a different robots.txt file for each one. This module generates the robots.txt file dynamically and gives you the chance to edit it, on a per-site basis, from the web UI.

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5 Related links
Displays links related to content.

The related links module enables nodes to display related URLs to the user via
blocks. Related links can be defined in 3 ways:

* Parsed links: links that are retrieved from the body of a node.
* Manual links: links that are added manually.
* Discovered links: links that are discovered by the module using various
criteria, including the category terms of a node and suggestions provided by
the search module (when enabled).

The related links module allows for flexibility in creating blocks for each type
of related links or creating blocks for a combination of link types.

Again this module reinforces relevancy and provides a nice way to interweave internal relevant content, depending on the size of your site you will find yourself manually entering a couple of links and letting it discover a few others. Make sure you place the links you want to appear at the top.

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6 service links
The service links module enables admins to add links to a number of social bookmarking sites, blog search sites etc. Includes sites are del.icio.us, Digg, Reddit, ma.gnolia.com, Newsvine, Furl, Google, Yahoo, Technorati and IceRocket.

The site owner can decide:
- To show the links as text, image or both.
- What node types to display links for.
- If the links should be displays in teaser view or full page view or both.
- If the links should be added after the body text or in the links section or in a block.
- If aggregator2 nodes should use link to original article aggregated by aggregator2 module.
- Decide what roles get to see/use the service links.

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7 Site map
This module provides a site map that gives visitors an overview of
your site. It can also display the RSS feeds for all blogs and
categories. Drupal generates the RSS feeds automatically but few seems
to be aware that they exist.

The site map can display the following items:

* A message to be displayed above the site map
* The latest blogs.
* Any books that optionally will be displayed fully expanded.
* Any menus that will be displayed fully expanded.
* Any categories, i.e vocabulary, with all the terms expanded.
Optionally with node counts and RSS feeds.
* A syndication block, the "more" link goes to the site map.

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8 Search 404
Instead of showing a standard "404 Page not found", this module performs a search on the keywords in the URL, e.g. if a user goes to http://example.com/does/not/exist, this module will do a search for "does not exist".

It includes beta stage search engine keywords detections.

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9 Url List
Creates a list of node URLs at /q=urllist.txt or (/urllist.txt for clean URLs) for submitting to search engines like Yahoo! Site Explorer.

urllist.txt is listed as a valid feed for submitting all your site's URLs through your collection of "My Sites" at Yahoo!. Yahoo has some history of buggy anonymous submission, so you often have to be logged in to your Yahoo! account to submit your site to their Site Explorer service. As of version 5.x-2.0, URL list supports automatic update submission through the Yahoo Update Notification service.

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10 Alinks
Allows users to associates defined text to links.
This module is based on the wordpress module “alinks”. Very easy to use, just enter your normal content and setup the terms/links you want on your site through the administration interface.

Main features:

- Replace terms in the content body with alink.
- Does not change the node body as it is executed on display only.
- Can set the amount of occurrence to change.
- Can set on which content type it will be affected

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There are many more seo modules available, you can choose from them according to requirement of your website.