i. Add your link (free)

• Google Search Engine Crawler
• ExactSeek Search Engine Crawler
• Feed Shark: submits your RSS feed to 21 RSS Directories for free.
• Search AllinOne MetaSearch!: combining the power of all the worlds best search engines into one.
• Yahoo Search Engine Crawler = Yahoo + Altavista + All The Web
• Search engines (general search): Search AllinOne MetaSearch!: combining the power of all the worlds best search engines into one, AltaVista, AllTheWeb, Gigablast, Google, HotBot, Lycos, MSN, Teoma, WISEnut
• Searchengine Channel: Search engine optimization articles, SEO tutorials, website promotion tips & strategies
• Top Directories with free web site submission 
• Web directories: Best of the Web!, WebSavvy, About, GoGuides, ODP, Yahoo!
• An impressive list of link submission directories

• @-web - Suchmaschinen aktuell: an overview of German, European and international search engines, search engines news etc.
• Abacho.de Search Engine Crawler
• rankingCheck: die wichtigsten Kataloge: die wichtigsten Webkataloge ohne Re-direct, mit PageRank 5 und höher, sortiert nach PageRank.
• SuchFibel.de - 2700 search engines; fast 2700 Suchmaschinen übersichtlich sortiert und nach Stichwörtern durchsuchbar
• SuchLexikon.de is a catalog of German search engines; ein durchsuchbares Verzeichnis spezieller deutschsprachiger Suchmaschinen, Kataloge, Verzeichnisse und Linksammlungen.

ii. Search engines and the optimization of the search engine submission

i. SEO Tools

• 99 Free SEO Tools
• DevToolz - Google Pagerank Lookup, Link Popularity Checker, WhoIs Lookup.
  Alternative: RIPE Whois Database.
• Dogpile: Search Comparison Tool
• icon interactive Link Popularity Tool is an all in one tool to check the number of pages that link to you in AlltheWeb, AltaVista, Google, HotBot, MSN Search, and Yahoo!, as well as check for your site's presence in DMOZ and Zeal.
• Google's PageRank - Calculator, Google PageRank Calculator (Alternative)
• Keyword Density Analyzer
• Marketleap Search Engine Marketing Tools and Search Engine Keyword Position Analyzer: Link Popularity Check, Search Engine Saturation, Keyword Verification - professional tools for checking the ranking of your site and its position in search engines.
• NicheBot - Keyword Database (Wordtracker keywords): NicheBot.com combines the Overture keyword selector tool with tools for Keyword Analysis, Keyword Thesaurus, Keyword Lateralus (for lateral thinking ideas for keywords) and even a tool to check keywords and site rankings according to Google. (via www.yellow-llama.com/blog/)
• Overture Keyword Selector Tool
• Page Rank Checker
• Page Rank Update List History - PageRank - PR
• Poodle Predictor - see your site like Google does. Simulate search engines and predict your Google listings
• SearchBliss: Link Popularity Check, SE Saturation-Index Check, Keyword Verification Check, Meta Tags Optimization, SEO - Optimization Articles, Unbranded SEO Tools
• Search Engine Optimization (SEO): SEO Chat, SEO Scanner - Pros' SEO Tool & The Pages Indexed, Backlinks Domain, Pagerank, Allinanchor, Keyword Density - (registration needed) Search Engine Optimization Tools & Resources. The internet's most popular and powerful suite of SEO Tools. Link Popularity, Meta Tag Generator, Domain Typos - find common misspellings of domains, Keyword Density - determine a URL's keyword densities, Google Keywords - find relevant & popular search-terms, Overture Keywords - Query Overture's database of searches, PageRank Search - Search with PageRank supplemented results, PageRank Lookup - Check PageRank of multiple URLs, Future Pagerank - Check PR across Google's data-centers, Site Link Analyzer - Analyze outbound links & anchor text, Meta Analyzer - Analyze a website's META tags, Keyword Optimizer - Remove duplicates & sort keyword lists alphabetically.
• SEO Tool for Yahoo Search Engine - Free online SEO tool to check the position of your website in the search engine of Yahoo™.
• SiteOMetrics: Link Popularity, SE Saturation, Keyword Position / SERP, Google PageRank, Bulk Google PageRank, Google PageRank: Indexed Pages, Alexa Rank, Bulk Alexa Rank
• Spider emulator
• This is how a search engine robot sees your web-site
• Yahoo! & Google Search Comparison
• Google PageRank Verifier
• Ranking Check

ii. SEO References

• Database of Web Robots, Overview
• Google Ranking Factors alleged positive and negative on- & off-Page SEO Google Ranking Factors in an overview
• How to Find a Great Domain Name
• Searchengine Watch - the source for search engine marketing and a magnificent reference on search engines.
• Search Engine Optimization Forum
• Search Engines Overview
• Search Engine Visibility - Do You Measure Up?, Common SEO Mistakes and other articles provided by AllStar Webmarketing Blog
• Tools You Might Have Missed is a collection of useful research tools, which use Google API and Yahoo API.
• The Anatomy of a Large-Scale Hypertextual Web Search Engine - this is how Google works
• What People Search For - Most Popular Keywords.
• Why Blogs Rank High In Search Engines
• Kostenloser Suchmaschinen-Marketing-Kurs
• Keyword Database - Keyword-Datenbank
• Suchmaschinen Tutorial
• Suchmaschinenoptimierung Grundlagen, SEO-Artikel: Artikel über die Linkpopularität, SEO, Suchmaschinenmarketing, Suchmaschineneintrag, Suchmaschinenoptimierung und Keywordrecherche.

SEO-specialists know...

• Great Site Ranking in Google The Secrets Out: Google have recently filed a US patent which reveals a great deal of how they rank your web site. Some of it you could never of guessed at...
• How To Get Slashdotted is an article which describes the methods of driving traffic to your site