SEO Bulletin

Domain Check and Value Estimation Tool - dnScoop.com attempts to estimate a value for an established website or a domain name by using factors such as:

Links pointing to the domain
Popularity of the domain
Age of the domain
Pagerank of the domain
Traffic to the domain
and more…

http://www.dnscoop.com/

For keyword research check out these tools:

Microsoft adCenter Labs
Google Keyword Tool

Here is a list of validators and checkers from WDG: Validators and Checkers

What does this tool do? This tool analyzes a web page, searching for characteristics that search engines could consider spam. If you don’t know what “search engine spamming” means or if you want to know how this tool works, you can read the Spam detector FAQ.

http://tool.motoricerca.info/spam-detector/

Browse the web and see the Page Rank of all links in a page at http://www.webmastereyes.com/

Google Analytics tells you everything you want to know about how your visitors found you and how they interact with your site. You’ll be able to focus your marketing resources on campaigns and initiatives that deliver ROI, and improve your site to convert more visitors.
Source: http://www.google.com/analytics/

Use this Keyword Difficulty Check Tool to see how difficut it would be to rank for specific keywords, or keyword phrases.

http://www.seologs.com/keyword-difficulty.html

You can find a small selection of interesting SEO tools at http://www.submitexpress.com/

Type and follow this URL into your web browser:

http://api.my.yahoo.com/rss/ping?u=url to your blog feed

Example:
http://api.my.yahoo.com/rss/ping?u=http://www.seobulletin.com/blog/feed/

Unique Linking Domains Tool on Post Trades forum shows you how many unique sites are linking to your domain.

http://www.posttrades.com/forum/

Link Harvester Tool: unique linking domains, C blocks, and more.

http://www.linkhounds.com/link-harvester/backlinks.php

For access to a number of search engine optimization tools such as:
–Search Engine Spider Simulator
–Backlink Anchor Text Analysis
–Backlink Builder
–Keyword Density Cloud
–and more go to http://www.webconfs.com/

Keep tabs on SERPs with Google Alerts.

Source: SEOMOZ.org

http://www.seomoz.org/articles/search-ranking-factors.php

Keyword Difficulty Tool

This tool measures the relative difficulty of optimizing for a particular keyword phrase by analyzing such metrics as number of results for the terms in quotes, number of pages with the keyword phrase in the title, bid amounts at Overture, and more.

Check Class C IP Address

Search Engine Simulator - spider viewer
Search Engine Simulator
Search Engine Spider Simutator
Poodle Predictor
SEO-Browser
Spider Simulator

Search Engine Saturation Tool [SEOGUY]
Search Engine Saturation

Search Engine Positioning Tool [SEOGUY]
SERP Check on Google, MSN, and Yahoo.

Google Datacenter Checker
Datacenter Quick Check [SEO GUY]