SEO Digger - you can find out for which keywords your site ranks high enough to be in Google Top 20. You can analyze your own sites as well as sites of your competition

Search engine Saturation;  Check your Search Engine Saturation levels and compare your website to competitors

Blog Juice Analysis - compare Blog to others on a variety of factors

SEOmoz Page Strength - designed to satisfy the curiosity of webmasters, surfers and web marketing professionals seeking a better metric to quickly assess a site/page's relative importance and visibility.

Xinu - Check your PageRank, backlinks and much more; overview tool.

Keyword Analysis - page an KW analysis tool from Dave Naylor

Authority Finder - compare top ranking sites on Google and Yahoo in anodal graph.

Web Spam Detector - take a quick look for potential flags a web page may have.

Digging deeper ; URI Valet - Check Server Header - Batch Server Headers - Cool Cache checker -

Spy Fu - lets you see which keywords your competitors are buying and which ones they optimize their site for.

Abakus - Analyzes - analyze a webpage for top keywords and phrase usage.

Advanced Google search tool uses some of the advanced search parameters from Google to create a complex search that can be useful for keyword research.

SEO Digger - you can find out for which keywords your site ranks high enough to be in Google Top 20. You can analyze your own sites as well as sites of your competition

MSN Keyword Trends - forecast the search volume and demographic predictions of your selected list of keywords. (also see MSN SERP Cluster tool)

Key Compete - KeyCompete is an online keyword research tool that identifies the keywords your competitors are using in their pay-per-click campaigns. KeyCompete also identifies the competition that is bidding on your keywords. |

Suggestion Tools; Overature Suggestion | Miva Suggest | More Suggestions | Word Tracker FREE | Keyword Discovery FREE  | nXplorer | SEO Book tool | iWeb Tool | SEO Book tool (new) |

Hub Finder - looks for sites which have co occuring links to related authoritative websites on a particular topic.

Bad Neighbourhood Checker - scans the links on your website, and on the pages that your website is linking to, and flag possible problem areas.

Link Diagnosis -show you all the important information about your competitor's links. The report includes pagerank, anchor texts, no-follow information and more.

Web Spam Detector - take a quick look for potential flags a web page may have.

Link Valet - analyzes both internal and external links for a given webpage.

Backlink Builder - searches for websites of the theme you specify that contain keyphrases like "Add link", "Add site", "Add URL", "Add URL", "Submit URL", "Add Article" etc.

Backlink Analyzer - another great tool from Aaron Wall (free download) 

Directories; SEO Friendly Directories and Directory Critic - Niche directories - More Niche Directories - List of Paid Directories - Hub Finder -

Article Submissions;  Article Directories and Niche distribution Article Submission Services - Article Marketer |

Blogs - always a good way to do SMM and Link building at the same time as stayin in tune; Blog Hub | Technorati | MyBlogLog | Blog Catalog | Google Blog Search | Blog Juice Analysis 

Social Media - Big List of Social media- Here on the trail

Meta tag generator; - Web Page Speed; - Robots.text Creator - Cloaking Checker - My IP Nieghbours (checks sites on a server) - Web Spam Detector - Domains on My IP -

Domains; Sedo - Domain Bot - Domain Tools - Reverse IP lookup - Reverse IP 2 - My IP Nieghbours (checks sites on a server) -

PPC Tools ; Overture Bid Calculator; | Adwords Keyword calculator 

Press Release sources;

PR Web/ | Business Wire / | Iinternet.com/ | PR News Wire / - Big list PR Sites -

SEOpen - 23 metrics from back links, whois and checking robots.txt.
SEO For Firefox -Aaron Wall’s tool - 13 different signals
yExplore - easy right click access to Yahoo Site Explorer info.
SeoQuake - Interesting tool for analyzing search results - Don’t overdo it.
KGen -Keyword generator analyzes a page for keyword frequency and placement.
Niche Watch Tool - Checks back links, indexed pages, keyword frequency and several other SEO signals.
MetaTags - Offers a side bar menu showing a web page’s meta data, links, keyword frequency and others.
Search Status - Highlights nofollow links, back links, indexed pages, Alexa and Compete rankings.
Prefbar - Toggle JavaScript, Flash and images as well as spoof user agent.

tnx to TopRank