Linke Explorer
MOZ Link explorer offers the world’s best backlink checker, which visits the URL you enter, can help you monitor your backlink profile so you are immediately notified should any poor-quality sites link to you.

Spider Food
Over 160 pages of search engine optimization, web site promotion, and submission tutorials plus a discussion forum.

Search Engine Submission:

Scrub The Web

Promotion World
Articles, tutorials, everything you need to know about promotion. If you’re just starting out, be sure to go through their tutorial first. Free! highly recommended

Search Engine Watch
The first place to go to learn all about search engines. This site explains the differences between search engines and directories. highly recommended
Interested in low-cost or free Internet advertising? ReciprocalLink.Com is an information center for reciprocal links, where webmasters link to each other for mutual benefit. They also lists websites that are “reciprocal link-friendly”. Add yours today!

Submit Corner
Search Engine Optimization and Placement Full featured suite of free online web tools including META Tag Generator and Scanner, Search Engine Submission, Robots Generator, Link Scan, and guides to targeting your market with search engines.

Free Advertising Sites to Promote Your Website Online: